8-optical power calculation training

HUAWEI

WDM OPTICAL POWER

MANAGEMENT TRAINING

© 2013 Huawei Technologies Co.,Ltd.

All Rights Reserved No part of this manual may be reproduced or transmitted in any form or by any means without prior written consent of Huawei technologies Co., Ltd

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Notice The information in this manual is subject to change without notice, every effort has been made in the preparation of this manual to ensure accuracy of the contents, but all statements, information, and recommendations in this manual do not constitute a warranty of any kind, express or implied.

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Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.

OptiX WDM Product Optical Power Calculation

Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved. Page1

Foreword

� When commissioning or planning the WDM network, we

need to calculate the optical power. This Course will

introduce the method of OptiX WDM Product power

calculation.

1


About This Course

� This Course is based on:

� OptiX BWS 1600G Hardware Description

� OptiX Metro 6100 Hardware Description

� OptiX OSN 6800 Hardware Description

� OptiX OSN 6800 Commissioning Guide

� OptiX OSN 68003800 Optical Power Calculation


Objectives

� Upon completion of this course, you will be able to:

� Illustrate the relation of each reference point.

� List the common indices on optical power calculation.

� Calculate the optical power.

2


Contents

1. Basics

2. Power Calculation


Contents

1. Basics

1.1 Review of the signal flow

1.2 Basic Concepts

3


Review of Signal Flow

OTUM40

M40

M40

D40

F

I

USC1

OA

SC2

OTU

OTU

OTU

OA OA

OA

F

I

U

F

I

U

F

I

U

OA

M40

D40

OTU

OTU

OTU

OTU

M40

M40OA

OTM1OTM1 OLAOLA OTM2OTM2

SC1


Review of Signal Flow (Cont.)

F

I

U

F

I

U

SC2

MR2

OA

OAMR2

MR2

MR2

OA

OA

FOADMFOADMOTU

OTU

OTU

OTU

OTU

OTU

OTU

OTU

4



F

I

U

F

I

U

SC2

ROAM

OA

OA OA

OA

ROADM:ROADM:(ROAM)(ROAM)

ROAM

M 4 0D40M 4 0D40

OTU

OTU

OTU

OTU

…… ……



F

I

U

OA

OA

WSD9 WSM9

WSM9 WSD9

OA

OA

F

I

U

M 4 0M40 M 4 0D40

M40 D40 M40 M40

ROADM:ROADM:(WSD9+WSM9)(WSD9+WSM9)

OTU

OTU

OTU

OTU

OTU

OTU

OTU

OTU

OTU

OTU

OTU

OTU

OTU

OTU

OTU

OTU

……

…… ……

……

5



F

I

U

OA

OA

WSD9 RMU9

RMU9 WSD9

OA

OA

F

I

U

M 4 0D40

M40 D40

ROADM:ROADM:(WSD9+RMU9)(WSD9+RMU9)

MR4

MR4

OTU

OTU

OTU

OTU

OTU

OTU

OTU

OTU

OTU

OTU

OTU

OTU

OTU

OTU

OTU

OTU

……

…… ……

……


Units

� mW

the unit of optical power

� dBm

the unit of optical power

� dB

the unit of gain or attenuation

of optical power

Basic Concept

P(mW)

1(mW)

Calculation

P1(dBm)

P2(dBm)

P1(mW)

P2(mW)

� P (dBm) =10lg

� P (dB)＝10lg =10lg

� -10dBm = mW

� 0dBm = mW

� 10dBm= mW

� 20dBm = mW

� 20dBm-10 =10dBm

6


Formula

The situation of N wavelengths

Ptotal (dBm) ＝Psingle (dBm) +10lgN(dB)

P1

Ptotal

P2

Suppose P1=P2=Psingle

Ptotal (mW) ＝ P1 (mW) + P2 (mW)

Ptotal (dBm) ＝Psingle (dBm) +10lg2(dB)


Tips on Optical Power Calculation� Optical power values expressed in dBm can be subtracted from each other but

cannot be added to each other.

� Optical power values expressed in dBm can be added to each other only after they are

converted into values expressed in mW.

� The result of one value expressed in dBm minus another value expressed in dBm is

expressed in dB. The result of one value expressed in dBm minus another value

expressed in dB is expressed in dBm. For example: 5dBm－3dBm＝2dB; 5dBm－3dB＝

2dBm.

P (？？) ＝ P1 (dBm) － P2 (dBm)The optical power values expressed in dBm can be added to or subtracted from

each other only after they are converted into values expressed in mW.

P (dB) ＝10lg －10lg = 10lgP1(mW)

1(mW)

P2(mW)

1(mW)

P1(mW)

P2(mW)

P (dB) ＝ P1 （dBm) － P2 (dBm)

7


Tips on Optical Power Calculation (2)� The following are some values that are frequently used during calculation of total

multiplexed optical power:

10lg2=3 10lg4=2*10lg2=6 10lg32=5*10lg2=15

10lg10=10 10lg40=10lg(4*10)=10lg4+10lg10=16

� Quiz: If the nominal single-wavelength optical power of an 80-channel WDM

network is +4 dBm, what is the total multiplexed output optical power expressed in

dBm?

� Pmultiplexed = 10lg(80*Psingle (mW)) = Ptotal (dBm) + 10lg(8*10)

= Psingle (dBm) + 10lg8 + 10lg10

= 4 + 9 + 10 (dBm) = 23 (dBm)


Common Specifications� Optical power calculation involves three common specifications: insertion loss, optical amplifier

unit parameters, and OTU parameters.

� For the common specifications, you can refer to the following documentation:

� Approach 1: Refer to section "Technical Specifications" in the Product Description manual.

� Approach 2: Refer to Appendix D "Quickfinder of Board Specifications and Functions" in the

Hardware Description manual.

� Approach 3: Refer to section "Board Specifications" in the board description chapter in the

Hardware Description manual.

� For the OAU parameters, you can also refer to the Commissioning Guide.

The manuals of WDM products are available on Huawei Support website. You can obtain them

from the following directory:

8


Insertion Loss

� The loss of output optical power after the optical signals of

each channel pass through the corresponding channels.

Passive component

PoutPin

Insertion Loss (IL) = Pin–Pout

Unit: dB


Common Specifications

9


Common Specifications� Insertion loss of DCMs is a critical specification for optical power calculation. The DCM

insertion loss specifications of each WDM product are provided in section "Technical

Specifications" in the Product Description manual of the product.


OAU Parameters � Input optical power ①

� Output optical power ②

� Maximum single-wavelength output optical power ③

� Typical single-wavelength output optical power ④

� Gain

OA

Pout ②Pin ①

Pout ③

Total gain of the OAU (dB) = Pout ② (dBm) – Pin ① (dBm)

Single-wavelength gain (dB)= Pout ③ (dBm) – Pin ④ (dBm)

Pin ④

10


Common Specifications� For OAU specifications such as the input and output optical power range

and gain range, refer to the Hardware Description manual.

Note: For OAU specifications, you can also refer to Appendix D "Quickfinder of Board

Specifications and Functions" in the Hardware Description manual.


Common Specifications� For OAU specifications such as the maximum single-wavelength output optical power and typical

single-wavelength output optical power, refer to section "Commissioning the Optical Power of the

EDFA" in the Commissioning Guide.

11


Common SpecificationsSection "Commissioning the Optical Power of the EDFA" in the Commissioning Guide

Note: For OAU specifications, you can also refer to Appendix D "Quickfinder of Board Specifications and Functions" in the Hardware

Description manual.


Characteristics of OTU

� Mean Launch Power

� Receiver sensitivity: A

� Receiver overload: B

Recommended Receiving Power Range: A+3(dBm) ~ B-5(dBm)

The preceding specifications vary with the type of WDM- and client-side

optical modules on the OTU and the transmission distance. For the board

specifications of a WDM product, refer to section "Board Specifications" in

the Hardware Description manual of the product.

12



� Example of LSX

board

specifications

applied to the

OptiX OSN 6800

� The table on the

right shows the

specifications of

the optical module

on the client side.



� Example of LSX

board

specifications

applied to the

OptiX OSN 6800

� The table on the

right shows the

specifications of

the optical module

on the WDM side.

Note: For board specifications, you can also refer to Appendix D "Quickfinder of Board Specifications and Functions" in the Hardware Description manual.

13


Summary

� This chapter describes the following common specifications

used in optical power calculation of boards of WDM

products:

� Board insertion loss

� OAU parameters

� OTU parameters

� Section "Technical Specifications" in the Product

Description manual of each WDM product describes the

board parameters of the product.


Questions

� What are the units related to optical power?

� The conversion between mW and dBm?

� If the input power of each channel is –4 dBm, what’s the value of

input power for 40 wavelengths?

14


Contents

1. Basics

2. Power Calculation


Contents

2. Power calculation

2.1 Power calculation of OSC

2.2 Power calculation of Main Path

15


� Typical Launch Power

SC2: 0 ~ -4

SC1: 2 ~ 4.5dBm

� Sensitivity of SC1/SC2: -48dbm

� Receiving Power＝Launch Power - Loss of Fiber - 2•IL of FIU.

Power Calculation of OSC

TM RM

SC1/2SC1 SC1/2SC1

F

I

U

F

I

URM TM

2dBm

40km (12dB)

IL:1.5dB

0.5dBm -11.5dBm -13dBm

IL:1.5dB


Main-Path Optical Power Calculation—Basic Concepts

� OAU gain range:

� A gain range that depends on the hardware performance of the OAU. For the value of the

gain range, refer to the product manual.

� Typical gain of the OAU:

� The result of the nominal single-wavelength output optical power minus the nominal single-

wavelength input optical power after the input and output optical power of the OAU are

adjusted to the nominal values.

� Configurable gain range of the OAU:

� In actual applications, the configurable gain range of the OAU does equal the OAU gain

range. The configurable gain range of the OAU equals the OAU gain range minus the

passthrough insertion loss between the TDC and RDC optical interfaces. This formula

applies to the application scenario where a DCM is connected between the TDC and RDC.

For example, if the gain range of an OAU is 20–31 dB and the insertion loss between the

TDC and RDC is 5 dB queried on the T2000, then the configurable gain range of this OAU

is 20–26 dB (actually 15–26 dB. Because the gain value smaller than 20 dB is not

configurable on the T2000, the lower limit of the gain range does not change).

16


Main-Path Optical Power Calculation—Basic ConceptsSteps:

� Adjust the VOA to obtain –16 dBm nominal

single-wavelength input optical power of the

OAU. Set the gain to the typical gain value 20

dB to obtain +4 dBm nominal maximum

single-wavelength output optical power of the

OAU.

OAU101

PA BA③

⑤

DCM(B)

� If the input optical power fails to be adjusted to the nominal value, set the gain of the OAU to obtain the nominal output optical power. In this case, the configurable gain range of the OAU need be calculated. The configurable gain range of the OAU equals the OAU gain range minus the passthrough insertion loss between the TDC and RDC optical interfaces. For example, if the insertion loss between the TDC and RDC is 5 dB (it approximates the DCM insertion loss plus the fiber connector insertion loss) queried on the T2000 and the gain range of an OAU is 20–31 dB, then the configurable gain range of this OAU is 20–26 dB.

� If the single-wavelength output optical power can reach up to only –20 dBm, after the configurable gain range is calculated, 24 dB gain is required if the single-wavelength output optical power is the nominal single-wavelength output optical power plus 4 dBm. The 24 dB gain is within the configurable gain range 20–26 dB of the OAU. Hence, set the gain of the OAU to 24 dB.

� In the rare case that the gain value to be set is beyond the configurable gain range, it indicates that the client fiber attenuation is much larger than the designed value. In this case, stop the commissioning and notify the customer to solve the fiber attenuation problem.


Station A Station B

40km（12dB）

� The distance between station A and station B: 40km, line attenuation: 12dB.

� The same board configuration of station A and station B :

� Transmitting end: OBU101.

� Receiving end: OAU101.

OTM OTM

� Network topology

Power Calculation of Main Path - OTM

17


To station B

② ③ ④

OTU

M40

M40 OBU101

F

I

U

① ⑤

① Suppose Typical Launch Power of OTU: -2dBm.

② Min. insertion loss of VOA : 2dB.

③ IL of M40: 6.5dB.

④ OBU101 nominal individual channel input/output Power-20/0dBm, typical gain: 20 dB.

⑤ IL of FIU:1.5dB.

VOA

� Signal flow and related indices at the transmitting side of station A


Notes: The VOA is commonly placed after the output interface of each OTU board in the signalflow for Metro/NG WDM. The VOA is commonly placed after the M40 for the LH-DWDM


② ③ ④

OTU

M40

M40

F

I

U

①

To station B

� Typical optical power of the reference points at the transmitting side

of station A – Single Channel

-2dBm -20dBm 0dBm -1.5dBm


OBU101

18


② ③ ④

M40

M40

F

I

U

①

� Ptotal (dBm)＝＝＝＝Psigle (dBm) + 10lgN (dB)

OTU

OTU

-2dBm -20+10lgN 0+10lgN -1.5+10lgN

To station B

� Typical optical power of the reference points at the transmitting side

of station A – Multiplex Channels


OBU101


Station A Station B

� The launched optical power of station A : -1.5+10lgN(dBm).

� Attenuation of the line fiber: 12dB.

� The receiving optical power of station B: -13.5+10lgN(dBm).

OTM OTM40km（12dB）

-1.5+10lgN -13.5+10lgN


� Network topology and the line optical power

19


① IL of FIU:1.5dB.

② Min. IL of VOA : 2dB.

③ OAU101 nominal individual channel input/output Power -16/4dBm, typical gain: 20 dB.

④ IL of D40: 6.5dB.

⑤ Typical receiving optical power of OTU: -16dBm (APD), -9dBm (PIN).

① ②

M40

D40F

I

U

③ ④ ⑤

M40

D40

OTU

OTU

Fixed attenuator

-13.5+10lgN

� Signal flow and related indices at the receiving side of station B


From station A

OAU101


� If the input optical power of OAU is lower than the nominal power, VOA should be

removed.

④Psingle＝Ptotal - 10lgN - IL of D40.

① ②

From station A

M40

D40OPU03

F

I

U

③ ④

M40

D40

OTU

OTU

� Typical optical power of the reference points at the receiving side

of station B-13.5+10lgN -17+10lgN 4+10lgN -2.5dBm


OAU101

20


Power Calculation of Main Path - OLA

Station A Station C

OLAOTM OTM

Station B

40km（12dB）

� OBU103 is used at the transmitting side of station A & C.

� OAU101 is used in station B.

B

B

B DCM-B


60km（18dB）

+4+10lgN -11+10lgN

-1+10lgN-19+10lgN


OAU101

PA BAFrom station A

F

I

U

F

I

U

① ②

④

③ ⑤ ⑥

DCM(B)

� Typical optical power of the reference points from station A to station C

③ ⑤ OAU101 nominal individual channel input/output power: -16/+4dBm, gain range: 20~31dB.

④ IL of DCM(B): 5dB. ① ⑥ IL of FIU: 1.5dB.

Actual gain of OAU101 is 20dB.

-11+10lgN -16+10lgN +4+10lgN +2.5+10lgN

Power Calculation of Main Path - OLA

To station C

21


� Please calculate the optical power of each reference point① ② from station C to station A.

F

I

U

F

I

U①②

OAU101

BA

DCM(C)

PA

� Is it necessary to put VOA before OAU101?

� What is the actual gain of OAU101?

-20+10lgN

Questions

From station C

To station A

-21.5+10lgN

+4+10lgN


Station A Station C

FOADMOTM OTM

Station B

50km（15dB）


� OAU101/OBU103 is used at the station B.

� Two MR2 is used in station B.

B

B DCM-B


80km（24dB）

+4+10lgN -11+10lgN

Power Calculation of Main Path - FOADM

22


③ ⑤ OAU101 nominal individual channel input/output Power -16/+4dBm,

gain range:20~31dB.

④ IL of DCM(B): 5dB. ①⑩ IL of FIU: 1.5dB. ⑥⑧ IL of MR2: 1dB.

⑨OBU103 nominal individual channel input/output Power -19/4dBm.

① ② ③

④

⑤ ⑥ ⑦ ⑧ ⑨ ⑩

OAU101

PA BA

F

I

U

F

I

U

DCM(B)

MR2MR2

OTU

OBU103


OTU

OTU

OTU

-11+10lgN


From station A

To station C


①

②

③

④

⑤ ⑥ ⑦ ⑧ ⑨ ⑩

OAU101

PA BA

F

I

U

F

I

U

DCM(B)

MR2MR2

OTU

VOA

OBU103

OTU

OTU

OTU

-11+10lgN

-16+10lgN +4+10lgN -19+10lgN 4+10lgN

2.5+10lgN



From station A

To station C

+2.5

23


Station A Station C

ROADMOTM OTM

Station B

50km（15dB）


� OAU101/OBU103 is used at the station B.

� Two ROAM is used in station B.

B

B DCM-B


80km（24dB）

4+10lgN -11+10lgN

Power Calculation of Main Path - ROADM


③ ⑤ OAU101 nominal individual channel input/output Power -16/+4dBm,

gain range:20~31dB.

④ IL of DCM(B): 5dB. ①⑨ IL of FIU: 1.5dB. ⑩ IL of D40: 6.5dB.

⑥⑦ IL of ROAM: Mx-OUT:9dB, IN-DM:7dB, EXPI-OUT:14dB, IN-EXPO:3dB.

⑧ OBU101 nominal individual channel input/output Power -19/4dBm.

① ② ③

④

⑤ ⑥ ⑦ ⑧ ⑨

OAU101

PA BA

F

I

U

F

I

U

DCM(B)

ROAM

OTU

OBU101


OTU

OTU

OTU

-13+10lgN

Power Calculation of Main Path – ROADM 1

From station A

To station C

ROAM

D40 ⑩

24


①

②

③

④

⑤ ⑥ ⑦

OAU101

PA

F

I

U

F

I

U

DCM(B)

OBU103

-11+10lgN

-16+10lgN +4+10lgN

-3+10lgM

+4+10lgN

+2.5+10lgN


From station A

To station C

ROAM

OTU

OTU

OTU

OTU

ROAM

D40 ⑩

BA

⑧ ⑨

+1+10lgN’

-19+10lgN


-9.5dBm


③⑤ OAU1 nominal individual channel input/output Power -16/+4dBm, gain range:20~31dB.

④ IL of DCM(B): 5dB. ①⑨ IL of FIU: 1.5dB. ⑩ IL of D40: 6.5dB, IL of M40V: 8dB.

⑥ IL of WSD9: 8dB(IN-DMx,IN-EXPO).

⑦ IL of RMU9: 8.5dB(EXPI-OUT)


① ② ③

④

⑤ ⑥ ⑦ ⑧ ⑨

OAU101

PA BA

F

I

U

F

I

U

DCM(B)

WSD9

OTU

OBU103


OTU-11+10lgN


From station A

To station C

RMU9

D40 ⑩

OTU

OTU

M40

25


①

②

③

④

⑤ ⑥ ⑦

OAU101

PA

F

I

U

F

I

U

DCM(B)

OBU103

-11+10lgN


From station A

To station C

BA

⑧ ⑨


WSD9

OTU

OTU

RMU9

D40 ⑩

-16+10lgN +4+10lgN -19+10lgN

4+10lgN

2.5+10lgN

OTU

OTU

M40

-10.5dBm-4+10lgM


③⑤ OAU101 nominal individual channel input/output Power -16/+4dBm,

gain range:20~31dB.

④ IL of DCM(B): 5dB. ①⑨ IL of FIU: 1.5dB. ⑩ IL of D40/M40: 6.5dB.

⑥ IL of WSD9: 8dB(IN-DMx,IN-EXPO). ⑦ IL of WSM9: 8dB(AMx-OUT,EXPI-OUT).


① ② ③

④

⑤ ⑥ ⑦ ⑧ ⑨

OAU101

PA BA

F

I

U

F

I

U

DCM(B)

WSD9

OTU

OBU103


OTU

OTU

OTU-11+10lgN


From station A

To station C

WSM9

D40 ⑩M40

26


� Please calculate the optical power of each reference point (40 channels)

Questions

① ② ③

⑥F

I

U

F

I

U

OBUC01

-12+10lgN

From station A

To station C

⑧

⑨

WSMD4

OTU

OTU

OTU

OTU

D40⑤

M40

OAU101 WSMD4

④

-4

⑦

⑦ Optical power of adding wavelength.

⑧ Optical power of passing through.

⑩


Summary

� OSC Power Calculation

� OTM Power Calculation

� OLA Power Calculation

� FOADM Power Calculation

� ROADM(ROAM) Power Calculation

� ROADM(WSD9+RMU9) Power Calculation

� ROADM(WSD9+WSM9) Power Calculation

27

Thank youwww.huawei.com

28

1

OptiX WDM Product Optical Power

Calculation

P1

Welcome to this course on optical power calculation of OptiX WDM products.

In a WDM analog system, it's well known that optical power, optical signal-to-noise

ratio (OSNR), dispersion, and nonlinearity are four critical factors that influence the quality

of signals (QoS). Among these four factors, optical power is the most critical. During

deployment and maintenance of WDM equipment, the optical power of the equipment

must be calculated to ensure successful deployment and troubleshooting.

This course describes the method of calculating the optical power of OptiX WDM

products.

P2

This course is developed on the basis of the PowerPoint document OptiX OSN

3800&6800 Optical Power Calculation, with reference to the OptiX OSN 6800 Intelligent

Optical Transport Platform Commissioning Guide, OptiX OSN 6800 Intelligent Optical

Transport Platform Hardware Description, OptiX BWS 1600G Product Hardware

Description, and OptiX Metro 6100 Product Hardware Description. Should you have any

doubts on any specification or information mentioned in this course, refer to the

corresponding product manuals.

P3

Studying this course enables you to master the following knowledge:

- The relationship between the reference points in the signal flows of a WDM system.

- The common specifications for optical power calculation.

- Method of calculating the optical power at each reference point, with which you can

correctly calculate the optical power of a WDM product during deployment and

maintenance of the product.

P4

This document is organized into two chapters. Chapter 1 "Basic Knowledge"

describes the basic concepts of and tips for optical power calculation. Chapter 2 "Optical

Power Calculation" illustrates some examples to describe the method of optical power

calculation of WDM products in various networking modes.

2

P5

Let's start from Chapter 1. Chapter 1 is organized into two parts. Part 1 describes the

signal flows of WDM products; part 2 describes the basic concepts involved in optical

power calculation.

P6

Let's take a look at this networking mode. It is a common OTM-OLA-OTM networking

mode for WDM products. The signal flows in this networking mode are set forth below.

Signal flow from west to east: One or more wavelengths are added through one ore

more OTU boards at the OTM1 node (in the case of multiple OTUs, the wavelength added

through each OTU is different from the wavelengths added through the other OTUs). The

VOA for each OTU adjusts the optical power of the wavelength added through this OTU.

Then, the M40 board multiplexes the added wavelengths. The OA amplifies the

multiplexed optical signals so that the signals can travel over a long haul. At last, the FIU

board multiplexes the service signals with the OAM overhead signals. The multiplexed

signals travel towards east over the optical cable. This is the internal signal flow of a single

OTM as an optical NE (ONE).

The signals of the OTM1 node travel to the OLA node. The west FIU board at the OLA

node separates the overhead signals from the service signals. The SC2 board receives

and processes the overhead signals, and the VOA adjusts the optical power of the service

signals. Then, the OA unit further amplifies the optical power of the service signals. The

amplified optical service signals continue to travel eastwards to the east FIU board at the

OLA node. On the east FIU board, the service signals are multiplexed with the overhead

signals processed by the SC2 board. The multiplexed signals are fed to the optical cable

and continue to travel eastwards.

The signals sent from the OLA node travel over the optical cable to the downstream

OTM2 node. The west FIU board at OTM2 separates the overhead signals from the

service signals. The overhead signals travel to the SC1 board for processing. Because the

service signals travel over a long-haul optical cable, the attenuation of the service signals

is large. Hence, the OA must be used to amplify the service signals. Then, the D40

demultiplexes the multiplexed service signals into multiple wavelength signals. Each OTU

receives one wavelength. In addition, to ensure that the received optical power of the OTU

is within the proper range, the WDM-side IN optical interface of each OTU must be added

with a fixed optical attenuator.

At this point, the signal flow from the OTM1 node to the OTM2 node is complete. The

signal flow from OTM2 to OTM1 reverses the signal flow from OTM1 to OTM2.

P7

Now let's take a look at the internal signal flow of an FOADM node. The FOADM node

refers to a fixed optical add/drop multiplexer node. The overhead signal flow of service

signal propagation before the OA board at the FOADM node are the same as those at the

3

OLA node, which are omitted in this slide. Let's find out the differences between this slide

and the last slide.

The OA board amplifies the service signals. Then, the amplified service signals enter

the MR2 board for demultiplexing. The MR2 is a typical FOADM board. The FOADM

board serves to separate one or more wavelengths from the service signals and drop the

wavelength(s) from the local client equipment. The other wavelengths of the service

signals pass through the FOADM board and travel to the downstream. The MR2, as its

name implies, serves to separate two wavelengths from the service signals and drop the

two wavelengths from the local client equipment. The other wavelengths of the service

signals pass through the MR2 and travel to the downstream. In addition, multiple FOADM

boards can be cascaded, as shown in the figure in this slide. The second MR2 can further

separate two wavelengths from the wavelengths passed through the first MR2 and drop

the two wavelengths to the local client equipment. The remaining wavelengths pass

through the second MR2 and travel to the downstream. The local OTU board receives the

two wavelengths dropped from the second MR2. To ensure that the received optical

power of the OTU is within the proper range, the WDM-side IN optical interface of each

OTU must be added with a fixed optical attenuator.

The process of wavelength adding reverses that of wavelength dropping. The

principles of the two processes are the same. Not that to ensure that the optical power of

each added wavelength in the OA unit is a proper value, the OUT optical interface of each

OTU must be added with a VOA for optical power adjustment.

P8

Now let's take a look at the internal signal flow of an ROADM node. The ROADM

node refers to a reconfigurable optical add/drop multiplexer node. Compared with the

FOADM node, the ROADM node is advantageous in dynamic grooming of added/dropped

wavelengths from/to the local client equipment. The ROADM node selects different

wavelengths that travel towards different directions, whereas the FOADM node can select

only one fixed wavelength and grooms it towards one direction. Hence, the wavelength

grooming of the FOADM node is not flexible. Generally, the ROADM node can be formed

in three networking modes. Firstly, let's study the first networking mode of the ROADM

node, in which the ROADM node uses two ROAM boards. The signal flow in this

networking mode is set forth below.

See the following figure. Two ROAM boards are used together with the D40 board to

add/drop, pass through, and block a maximum of 40 service wavelengths. This realizes

the dynamic grooming of intra-ring service wavelengths.

In the wavelength dropping direction, the multiplexed optical signals received from

west are accessed to the main-path optical signals through the IN optical interface on the

west ROAM board. The west ROAM board evenly splits the main-path multiplexed optical

signals into two channels of signals. One of the two channels of signals is dropped to the

local D40 and then is output to the local OTU board. The other channel of signals passes

through the west ROAM board and travels to the east ROAM board.

4

In the wavelength adding direction, the optical signals sent from the local OTU board

directly travel to the 40 AM optical interfaces on the west ROAM board for multiplexing.

The west ROAM board can also multiplex the multiplexed optical signals received from

west with the multiplexed optical signals that pass through the east ROAM board, and

outputs the final multiplexed signals to the west optical amplifier board. The west optical

amplifier board amplifies the signals and sends them to the line. Note that during

multiplexing of the 40 channels of added optical signals with the signals that travel from

the upstream, a 2×1 optical switch on the west ROAM board can select from between

each monochrome wavelength that travels from the upstream and each wavelength that is

added from the local client equipment. This realizes the flexible selection between

passthrough and adding of wavelengths.

P9

Then, let's study the second networking mode of the ROADM node, in which the

ROADM node uses the WSD9+WSM9 board combination. These two boards are the

WSS board. The WSS board is used to drop (or add) any wavelength through any output

(or input) optical interface. In addition, the WSS board can demultiplex the received color

optical signals into any combination of wavelengths and outputs them through arbitrary

interfaces. This realizes the grooming between multiple wavelengths on the optical

multiplex section.

A single wavelength or a channel of multiplexed signals to be dropped to the local

client equipment is output through a wavelength dropping interface on the WSD9. In the

case of dropping a channel of multiplexed signals, the D40 board demultiplexes this

channel of multiplexed signals into single wavelengths and sends them to the local client

equipment through OTUs. In the case of dropping a single wavelength, the signal is

directly dropped from the WSD9 to the local OTU. The remaining signals after wavelength

dropping pass through the WSD9 board and travel to the downstream.

The signal flow of the WSM9 reverses that of the WSD9. A single wavelength or a

channel of multiplexed signals to be added from the local client equipment is input through

a wavelength adding interface on the WSM9. In the case of adding multiple wavelengths,

the M40 board multiplexes the multiple wavelengths into one channel of multiplexed

signals and sends it to the WSM9. In the case of adding a single wavelength, this

wavelength is directly added from the local OTU to the WSM9.

P10

Finally, let's study the third networking mode of the ROADM node, in which the

ROADM node uses the WSD9+RMU9 board combination. Compared with the second

networking mode, the WSM9 is replaced with the RMU9 of a lower cost in the third

networking mode. The RMU9 has only the wavelength adding and multiplexing functions

and does not have the wavelength selective grooming function that the WSM9 has. If the

RMU9 accesses multiple wavelengths, the M40 or an optical add/drop multiplexing unit

5

(such as the MR4 or MR2 board) multiplexes the multiple wavelengths into one channel of

multiplexed signals and sends it to a wavelength adding interface on the RMU9. If the

RMU9 accesses a single wavelength, this wavelength directly travels from the local OTU

to a wavelength adding interface on the RMU9.

P11

Now let's turn to part 2 of Chapter 1. Part 2 describes the basic concepts involved in

optical power calculation.

What units can optical power be expressed in? Optical power can be expressed in

mW, dBm, or dB. Generally, dB is used to express optical power attenuation or gain.

How are the units calculated? It's well known that mW is a basic unit to express power.

In fact, dBm is a unit calculated in this way: Suppose that P denotes a power value

expressed in mW. The result of 10 times of the logarithm of the ratio of P to 1 mW is the

power value expressed in dBm. The following is the calculation formula. dB is a unit

calculated in this way: Suppose that P1 and P2 denote two power values expressed in

mW. In this case, P2 is a certain number of mW or dB but not dBm higher or lower than P1.

The next slide explains the reason. The result of 10 times of the logarithm of the ratio of

P2 to P1 is the power value expressed in dB.

Let's try out a quiz. Use the preceding two formulas to calculate the results of the

following five test questions. When –10 dBm substitutes P in the formula, the result is 0.1

mW. Likewise, 0 dBm equals 1 mW; 10 dBm equals 10 mW; and 20 dBm equals 100 mW.

The answer to the last test question is: 20 dBm - 10 dB = 10 dBm. You can comprehend

this answer in this way: Because dB expresses the value of power gain or attenuation, 20

dBm is 10 dB larger than 10 dBm. That is, 20 dBm - 10 dBm = 10 dB. Transpose 10 dBm

and 10 dB in the equation, and the equation changes to 20 dBm - 10 dB = 10 dBm.

P12

Now let's study the formula for calculating total optical power, which is the most

frequently used in the WDM domain. It's well known that the optical power of each

wavelength of a WDM product must be flattened to the same value. Suppose that both the

optical power values P1 and P2 equal the single-wavelength optical power Psingle, then the

total optical power Ptotal equals two times of Psingle. Note that the all these power values are

expressed in mW. If they are expressed in dBm and dB, Ptotal = Psingle + 10lg2. Where,

Psingle is expressed in dBm and 10lg2 is expressed in dB. Likewise, if the number of

wavelengths of a WDM system is N, Ptotal = Psingle (dBm) + 10lgN (dB).

P13

Now let's summarize the basic concepts of and useful tips for optical power

calculation. They help in calculating optical power during deployment and maintenance.

Bear in mind the first tip for optical power calculation: Optical power values expressed

6

in dBm can be subtracted from each other but cannot be added to each other. When the

formula for calculating optical power values P1 and P2 expressed in dBm in the equation

substitutes P1 and P2 for subtraction, the calculated result of the equation can be

expressed in dB. Hence, optical power values expressed in dBm can be subtracted from

each other. When the formula for calculating optical power values P1 and P2 expressed in

dBm in the equation substitutes P1 and P2 for addition, the result of the equation cannot

be calculated. Hence, optical power values expressed in dBm can be added to each other

only after they are converted into values expressed in mW. The equation P(dB) = P1(dBm)

- P2(dBm) shows that the result of one value expressed in dBm minus another value

expressed in dBm is expressed in dB. After P and P2 are transposed, the equation

P2(dBm) = P1(dBm) - P(dB) shows that the result of one value expressed in dBm minus

another value expressed in dB is expressed in dBm.

P14

Bear in mind the second tip for optical power calculation: Remember some optical

power values that are frequently used.

It can be calculated that 10lg2 = 3. Hence, 10lg4 = 2 × 10lg2 = 6. Likewise, 10lg8 = 9,

10lg16 = 12, and 10lg32 = 15. It also can be calculated that 10lg10 = 10. Hence, 10lg20 =

10 + 10lg2 = 13, 10lg40 = 10 + 10lg4 = 16. Remembering these frequently used optical

power values helps you quickly calculate in your head some typical total optical power

values configured for WDM networks.

Let's do another quiz. Suppose that a WDM network is configured with 80 channels,

and the optical power of each channel is flattened to the same value +4 dBm. Calculate

the total optical power. By using the preceding two tips and the formula Ptotal = Psingle +

10lgN (N denotes the number of wavelengths), you can quickly calculate in your head the

total optical power Ptotal = 4+ 10lg80 = 4 + 10 + 10lg8 = 4+ 10 +9 = 23 dBm.

P15

Optical power calculation involves three types of common specifications: insertion

loss (IL), optical amplifier unit parameters, and OTU parameters.

For the common specifications, you can refer to the following documentation:

Approach 1: Refer to section "Technical Specifications" in the Product Description

manual.

Approach 2: Refer to Appendix D "Quickfinder of Board Specifications and

Functions" in the Hardware Description manual.

Approach 3: Refer to section "Board Specifications" in the board description chapter

in the Hardware Description manual.

For the OAU parameters, you can also refer to the Commissioning Guide.

The manuals of WDM products are available on Huawei Support website. You can

obtain them from the following directory:

Documentation → Optical Network Product Line → WDM → OptiX OSN 6800 →

7

Product Manuals

P16

Firstly, let's take a look at the first parameter involved in optical power calculation:

insertion loss (IL).

Definition of IL: The result of the input optical power Pin minus the output optical

power Pout when the optical signals travel over a passive optical component. IL is

expressed in dB. Why must it be a passive optical component? The reason is that to

ensure that the test result indicates the pure IL, the optical signals must not be

regenerated or amplified in the optical component.

P17

Take the MR2 board as an example. The IL between the IN and D1 optical interfaces

of the MR2 board is the same as that between the IN and D2 optical interfaces of the MR2.

The wavelength dropping IL is a maximum of 1.5 dB; the wavelength adding IL between

the A1/A2 and OUT optical interfaces is a maximum of 1.5 dB; and the IL between the MI

and OUT optical interfaces is a maximum of 1.0 dB.

P18

IL of dispersion compensation modules (DCMs) is a special specification of WDM

products, which is usually neglected when we concern about the specifications of various

boards. For the specifications of DCMs, refer to section "Technical Specifications" in the

Product Description manual. The section "Technical Specifications" also provides the

specifications of various boards.

The specifications of DCMs vary with the DCM type. For details, refer to the following

table.

P19

Then, let's take a look at the second type of parameters involved in optical power

calculation: optical amplifier unit parameters.

There are five common optical amplifier unit parameters: input optical power, output

optical power, nominal maximum output optical power, typical input optical power, and

optical amplifier gain.

For the definition of each specification, see the following optical amplifier unit diagram.

Both the input optical power and output optical power refer to the total optical power; both

the nominal maximum output optical power and typical input optical power refer to the

single-wavelength optical power. The total gain of the optical amplifier unit equals the

output optical power minus the input optical power. The single-wavelength gain equals the

single-wavelength output optical power minus the single-wavelength input optical power.

8

In the case of standard system commissioning, the single-wavelength gain equals the

nominal maximum single-wavelength output optical power minus the typical

single-wavelength input optical power. Because of the influence of optical amplifier unit

gain flatness, the total gain and single-wavelength gain might be different.

P20

After you learn the basic information about optical amplifier unit specifications, you

might like to know more details. For more details, you can refer to the Hardware

Description manual. The Hardware Description manual provides the specifications of

optical amplifier boards, such as the input and output optical power ranges and the gain

range. For such specifications, you can also refer to Appendix D "Quickfinder of Board

Specifications and Functions" in the Hardware Description manual. The specifications

vary with the type of the optical amplifier boards.

P21

For the commissioning specifications, namely, nominal maximum single-wavelength

output optical power and typical single-wavelength input optical power, of optical amplifier

units, refer to section "Commissioning the EDFA Optical Power" in the Commissioning

Guide.

The following table lists the typical single-wavelength input optical power values of

various optical amplifier boards used in the OptiX OSN 6800 products.

P22

The following table lists the nominal maximum single-wavelength output optical

power values of various optical amplifier boards used in the OptiX OSN 6800 products.

P23

Finally, let's take a look at the third type of parameters involved in optical power

calculation: OTU parameters.

There are three common OTU parameters: mean launched optical power, receiver

sensitivity, and receiver overload point. The recommended range of received optical

power is the receiver sensitivity plus 3 dBm receiver overload point minus 5 dBm. You

might ask: Why should the overload point be different from the sensitivity? Why must the

overload point minus 5 dBm? We can comprehend it this way: If the received optical

power of a board is close to the sensitivity, services are interrupted because of loss of

signals on the receive side; if the received optical power of the board is close to the

overload point, the services are interrupted and the optical module is damaged. Hence,

the received optical power of a board should be far from the overload point.

The preceding three specifications vary with the type of WDM- and client-side optical

9

modules on the OTU and the transmission distance. For the board specifications of a

WDM product, refer to section "Board Specifications" in the Hardware Description manual

of the product.

P24

Take the LSX board of the OptiX OSN 6800 product as an example. As provided in

the table on the right, the client-side optical module specifications vary with the module

type. In the case of a 10 km optical module with a rate higher than 10G, the maximum

mean launched optical power is –1 dBm; the minimum mean launched optical power is –6

dBm; the receiver sensitivity is –11 dBm; and the overload point is 0.5 dBm.

P25

Take the LSX board of the OptiX OSN 6800 product as an example. As provided in

the table on the right, the WDM-side optical module specifications vary with the module

type. In the case of an NRZ 40-channel optical module with 800 ps/nm dispersion

tolerance, the maximum mean launched optical power is 2 dBm; the minimum mean

launched optical power is –3 dBm; the receiver sensitivity is –16 dBm; and the overload

point is 0 dBm.

P26

This chapter describes the common specifications involved in optical power

calculation: insertion loss (IL), optical amplifier unit parameters, and OTU parameters.

Section "Technical Specifications" in the Product Description manual of each WDM

product describes the board parameters of the product.

P27

Now let's review what we have learned in this chapter. Answer the following two

questions.

Question 1: What are the measurement units for optical power? For the answer to

this question, you can refer to slide 11.

Question 2: If the single-wavelength input optical power is –4 dBm, what is the total input

optical power of a fully loaded 40-channel WDM system? You can use the formula in slide

12 and the example in slide 14 to calculate the answer to this question is 12 dBm.

P28

Now let's study Chapter 2: Optical Power Calculation.

10

P29

Chapter 2 "Optical Power Calculation" is organized into two parts: calculation of

optical supervisory channel (OSC) optical power and calculation of main-path optical

power.

P30

When calculating the OSC optical power, you can refer to the diagram of the OSC

signal flow between two adjacent nodes. The output optical power at the TM optical

interface of the OSC board SC2 ranges from 0 dBm to –4 dBm; that of the OSC board

SC1 ranges from 2 dBm to 4.5 dBm. Considering that the FIU imports 1.5 dB IL, you can

use this formula: Optical power at the receive end of the OSC (the RM optical interface of

the OSC board) = Optical power at the transmit end of the OSC (the TM optical interface

of the OSC board) - Fiber attenuation - 2 × FIU IL. For example, if the line fiber attenuation

between two adjacent nodes is 12 dB, then the budget optical power at RM equals: 2 - 2 ×

1.5 - 12 = –13 dBm. The supervisory signals are terminated and then regenerated at each

node. Hence, the supervisory system optical power is calculated between two adjacent

nodes.

P31

Then, let's study how to calculate the main-path optical power. First of all, let's learn

some basic concepts.

OAU gain range: A gain range that depends on the hardware performance of the

OAU. For the value of the gain range, refer to the Hardware Description manual. For

example, 20–31 dB.

Typical gain of the OAU: The gain capability of the OAU is a range. Hence, during

optical power commissioning, you need to set the gain of the OAU. Under normal network

conditions, the single-wavelength input and output optical power of the OAU can be

adjusted to the nominal values. At this point, the result of the nominal single-wavelength

output optical power minus the nominal single-wavelength input optical power is the

typical gain.

Configurable gain range of the OAU: In actual applications, the configurable gain

range of the OAU does not equal the OAU gain range. The configurable gain range of the

OAU equals the OAU gain range minus the passthrough IL between the TDC and RDC

optical interfaces. This formula applies to the application scenario where a DCM is

connected between the TDC and RDC. For example, if the gain range of an OAU is 20–31

dB and the insertion loss between the TDC and RDC is 5 dB queried on the T2000, then

the configurable gain range of this OAU is 20–26 dB (actually 15–26 dB. Because the gain

value smaller than 20 dB is not configurable on the T2000, the lower limit of the gain range

does not change).

11

P32

Now let's take a look at the procedure to commission and calculate the optical power

of an OAU.

Adjust the VOA to obtain –16 dBm nominal single-wavelength input optical power of

the OAU. Set the gain to the typical gain value 20 dB to obtain +4 dBm nominal maximum

single-wavelength output optical power of the OAU.

If the input optical power fails to be adjusted to the nominal value, set the gain of the

OAU to a proper value obtain the nominal output optical power. In this case, the

configurable gain range of the OAU need be calculated. The configurable gain range of

the OAU equals the OAU gain range minus the passthrough IL between the TDC and

RDC optical interfaces. For example, if the IL between the TDC and RDC is 5 dB (it

approximates the DCM IL plus the fiber connector IL) queried on the T2000 and the gain

range of an OAU is 20–31 dB, then the configurable gain range of this OAU is 20–26 dB.

If the single-wavelength output optical power can reach up to only –20 dBm, after the

configurable gain range is calculated, 24 dB gain is required if the single-wavelength

output optical power is the nominal single-wavelength output optical power plus 4 dBm.

The 24 dB gain is within the configurable gain range 20–26 dB of the OAU. Hence, set the

gain of the OAU to 24 dB.

If the gain value to be set is beyond the configurable gain range, for example, the

single-wavelength input optical power is –24 dBm, set the gain of the OAU to 28 dB obtain

the nominal single-wavelength output optical power. This is a rare case. It indicates that

the client fiber attenuation is much larger than the designed value. In this case, stop the

commissioning and notify the customer to solve the fiber attenuation problem.

Hence, if you set the gain of an OAU to a proper value, the output optical power of

this OAU equals the input optical power plus the gain of the OAU. You can also obtain the

gain of this OAU by querying on the T2000 the performance of the OAU. This document

tells you how to set the gain of the OAU, which helps in actual deployment.

P33

Let's take an example to study how to calculate the main-path optical power.

Suppose that nodes A and B form a point-to-point network. The two nodes are 40 km

away from each other; the fiber attenuation between the two nodes is 12 dB. The board

configuration of node A is the same as that of node B, that is, the OBU101 board is used

on the transmit side and the OAU101 is used on the receive side.

P34

Firstly, let's study the internal signal flow in the transmit direction of node A and the

relevant specifications. Suppose that the specifications of the boards are as follows:

- Typical output optical power of the OTU board: –2 dBm

- Minimum IL of the VOA: 2 dB

- IL of the M40: 6.5 dB

12

- Nominal input/output optical power of the OBU101: –20/0 dBm

- Typical gain of the OBU101: 20 dB

- IL of the FIU: 1.5 dB

P35

Based on the various specifications of boards, we can conclude that the output

optical power of the OTU is –2 dBm. When the optical signals travel over the VOA and

M40, the VOA adjusts the single-wavelength input optical power to the nominal value –20

dBm. The OBU101 provides the optical signals with 20 dB gain, and thus the output

optical power of the OTU reaches the nominal maximum single-wavelength output optical

power 0 dBm. After the optical signals are fed to the fiber line through the FIU, the line

optical power is –1.5 dBm.

P36

The last slide shows how to calculate single-wavelength optical power. Together with

the formula for calculating multiplexed optical power, the multiplexed optical power at the

OUT optical interface of the FIU equals –1.5 + 10lgN (dBm). Where, N denotes the

number of wavelengths.

P37

After the multiplexed signals are fed to the line, considering the line attenuation, the

optical power at the IN optical interface of the FIU at node B equals –13.5 + 10lgN (dBm).

P38

The method of calculating the optical power at node B is similar to that at node A.

First of all, query the specifications of each board.


- Minimum IL of the VOA: 2 dB

- Nominal single-wavelength input/output optical power of the OAU1: –16/4 dBm

- Typical gain of the OAU1: 20 dB

- IL of the D40: 6.5 dB

- Typical received optical power of the OTU: –16 dBm (APD) or –9 dBm (PIN)

P39

Use the preceding specification values to substitute the corresponding parameters in

the signal flow. The input optical power at the IN optical interface of the FIU equals –13.5

+ 10lgN (dBm). Because the IL of the FIU is 1.5 dB, the output optical power at the TC

optical interface of the FIU equals –15 + 10lgN (dBm) after the optical signals travel over

13

the FIU. Where, –15 dBm is the single-wavelength output optical power. Because the

inherent IL of the VOA is 2 dB, the input optical power of the OAU101 equals –17 + 10lgN

(dBm) after the optical signals travel over the VOA. Where, –17 dBm is the

single-wavelength input optical power, which is lower than the nominal single-wavelength

input optical power of the OAU101. Hence, based on the preceding method, you need to

set the gain of the OAU101 to 21 dB to ensure that the output optical power of the

OAU101 reaches the nominal gain which is +4 + 10lgN (dBm). After the optical signals

travel over the D40:

Single-wavelength optical power = Total optical power - 10lgN - D40 IL

Hence, the output optical power at any DM optical interface of the D40 is –2.5 dBm. To

ensure that the received optical power of the OTU is around the typical value, add a fixed

optical attenuator to the receive-side optical interface of the OTU. In the case of the PIN,

add a 7 dB fixed optical attenuator; in the case of the APD, add a 15 dB fixed optical

attenuator.

P40

Now let's take the OTM-OLA-OTM networking mode as an example to study how to

calculate the optical power at an OLA node. In the transmit direction of nodes A and C, the

OBU103 board is used. Hence, the nominal launched optical power of the OBU103 equals

+4 + 10lgN (dBm). Node A is 50 km away from node B, and the fiber attenuation between

nodes A and B is 15 dB. Hence, the received optical power, which is sent from node A, at

the IN optical interface of the west FIU at node B equals –11 + 10lgN (dBm). Node B is 80

km away from node C, and the fiber attenuation between nodes B and C is 24 dB. Hence,

the received optical power, which is sent from node C, at the IN optical interface of the

east FIU at node B equals –20 + 10lgN (dBm). Node B is an OLA, which uses the

OAU101 and type-B DCM.

P41

Optical power calculation of optical signals from west to east:

First of all, query the IL and optical power specifications of each board at node B.

- Nominal single-wavelength input/output optical power of the OAU1: –16/+4 dBm

- Gain range of the OAU1: 20–31 dB

- IL of Type-B DCM: 5 dB

- IL of the FIU: 1.5 dBThen, calculate the optical power at each reference point. The

received optical power at the IN optical interface of the west FIU equals –11 + 10lgN (dBm)

and equals –12.5 + 10lgN (dBm) after the optical signals travel over the FIU. After being

adjusted by the VOA, the input optical power of the OAU101 equals the nominal value –16

+ 10lgN (dBm). The gain range of the OAU101 is 20–31 dB. Considering the IL of the

DCM, the gain range of the OAU101 is 20–26 dB. Because the nominal output optical

power of the OAU101 is +4 + 10lgN (dBm), the gain need be set to 20 dB.

To calculate the optical power of optical signals in one direction of the OLA node to is

14

mainly to calculate the typical single-wavelength optical power of the optical amplifier

board. To debug board embedded software is to adjust the VOA before the optical

amplifier to make the optical power at each reference node reach the nominal value. The

optical power calculation of optical signals in the other direction of the OLA node is similar

to that in the preceding direction.

P42

Now let's do another practice on optical power calculation. Answer the following three

questions:

Question 1: Should a VOA be added before the OAU101?

Question 2: What is the desired gain to be set for the OAU101?

Question 3: What is the actual gain of the OAU101?

Answer to question 1: With the IL of the FIU considered, the single-wavelength output

optical power at the TC optical interface of the FIU is 21.5 dBm which is far lower than –16

dBm required. Besides, the VOA has 2 dB inherent IL. In the case of a mechanical VOA, it

must be removed on site. In the case of an electrical VOA (EVOA) board on site, it should

be retained for remote maintenance.

Answer to question 2: With the IL of type-B DCM considered, the configurable gain

range of the OAU101 is 20–26 dB. When the gain is set to 25.5 dB, the output optical

power of the OAU101 reaches the nominal value.

Answer to question 3: The actual gain of the OAU101 equals the configured gain plus

the IL of the DCM, which is 30.5 dB.

P43

Now let's take a look at how to calculate the optical power at an FOADM node.

The following figure shows the networking diagram. In the transmit direction of nodes

A and C, the OBU103 is used. The output optical power of the OBU103 is +4 + 10lgN

(dBm). At node B, the OAU101 or OBU103 and the type-B DCM is used. In addition, two

MR2 boards are used at node B to add and drop wavelengths. Node A is 50 km away from

node B, and the fiber attenuation between nodes A and B is 15 dB. Hence, the input

optical power at the IN optical interface of the west FIU at node B equals –11 + 10lgN

(dBm).

P44

Now let's take a look at the internal signal flow from east to west of node B and the

optical power.

First of all, query the specifications of each board at node B.

- Nominal single-wavelength input/output optical power of the OAU101: –16/+4 dBm

- Gain range of the OAU101: 20–31 dB

- IL of Type-B DCM: 5 dB

15


- IL between the IN and DM optical interfaces of the MR2: 1.5 dB

- IL between the IN and MO optical interfaces: 1 dB

- IL between the OUT and MI optical interfaces: 1 dB

- Nominal single-wavelength input/output optical power: –19/4 dBmThe input optical

power at the IN optical interface of the FIU equals –11 + 10lgN (dBm).

P45

Now let's calculate the optical power at each reference node. Based on the preceding

experience, it is easy to know that the optical power at the OUT optical interface of the

OAU101 equals +4 + 10lgN (dBm). The output optical power at the D01/D02 optical

interface of the MR2 is +2.5 dBm. Suppose that all OTUs at the receive end use the PIN,

add a 10 dB fixed optical attenuator to each OTU.

Then, let's calculate the single-wavelength optical power of passthrough wavelengths.

The single-wavelength optical power of passthrough wavelengths at the OUT optical

interface on the OAU101 is +4 dBm. Considering the optical power of passthrough

wavelengths of the two MR2 boards and 2 dB minimum attenuation of the VOA, the

single-wavelength optical power at the IN optical interface of the OBU103 should be a

minimum of 0 dBm. To make the single-wavelength optical power of the OBU103 reach

the nominal value, adjust the VOA between the two MR2s. That is, adjust the passthrough

wavelengths to make the single-wavelength optical power of the OBU103 reach the

nominal value. In the case of wavelength adding through the east-transmit OTU, adjust

the VOA at the wavelength adding channel to make the single-wavelength optical power

of the OTU reach the nominal value. In this way, the input optical power of the OBU103 is

–19 + 10lgN (dBm). The output optical power at the OUT optical interface of the east FIU

equals 2.5 + 10lgN (dBm).

The optical power calculation of optical signals in the other direction of the OLA node

is similar to that in the preceding direction.

P46

Finally, let's take a look at how to calculate the optical power at an ROADM node.

Again, a network formed by nodes A and B is considered as an example. The optical

amplifier board configuration of the two nodes in this example is the same as that in the

previous example. Node B uses two ROAM boards to add and drop wavelengths.

P47

The following figure shows the internal signal flow of ROADM node B. Likewise, refer

to the Hardware Description manual to query the IL and gain specifications of each board.

Note that the IL between each two optical interfaces of the ROAM board vary.

16

P48

The optical power calculation method of the optical amplifier board in this example is

the same as that in the previous example. The output optical power of the OAU101 equals

+4 + 10lgN (dBm). After the optical signals travel over the ROAM board, because the IL

between the IN and DM optical interfaces of the ROAM board is 7 dB, the output optical

power at DM equals –3 + 10lgM. Where, M denotes the number of the wavelengths

dropped through DM. Because the passthrough IL between the IN and EXPO optical

interfaces is 3 dB, the output optical power at EXPO on the west ROAM board equals +1 +

10lgN (dBm). After the wavelengths pass through the east ROAM board, the

single-wavelength optical power is –2 dBm. Adjust the internal VOA of the ROAM board to

make the single-wavelength output optical power of the OBU103 reach the nominal value

–19 dBm. Hence, the total input optical power of the OBU103 equals –19 + 10lgN (dBm);

the output optical power at the OUT optical interface on the east FIU equals +2.5 + 10lgN

(dBm).

The optical power calculation of optical signals in the other direction of the OLA node

is similar to that in the preceding direction.

P49

Now let's take a look at how to calculate the optical power at ROADM node B that

uses the WSD9+RMU9 board combination for wavelength adding/dropping. ROADM

node B that uses the ROAM board differs with ROADM node B that uses the

WSD9+RMU9 board combination in only that the IL of the WSD9+RMU9 boards is

different from the IL of the ROAM board. You can deduce the other cases by analogy.

P50

The optical power calculation of the signal flow shown in this slide is the same as that

in the case of ROADM node B that uses the ROAM board. Because the IL of the WSD9 is

different from the IL of the ROAM board, the optical power of passthrough wavelengths

equals –4 + 10lgN' (dBm). Where, N' denotes the number of passthrough wavelengths. In

this example, because of sufficient optical power budget, the optical power of each

wavelength of the OBU103 can be adjusted to the nominal value –19 dBm. If the optical

power budget id insufficient, add an optical amplifier board between the TOA and ROA

optical interfaces of the RMU9.

P51

Finally, let's take a look at how to calculate the optical power in the third ROADM

configuration scenario in which the WSD9+WSM9 board combination is configured. The

calculation method in this scenario is the same as that in the previous two scenarios,

which is omitted in this slide.

17

P52

You can calculate by yourself the optical power at each reference node in this

scenario.

P53

After studying this chapter, you should master the following knowledge:

Calculation of OSC optical power

Calculation of optical power of the OTM

Calculation of optical power of the OLA

Calculation of optical power of the FOADM

Calculation of optical power of the ROADM (ROAM)

Calculation of optical power of the ROADM (WSD9+RMU9)

Calculation of optical power of the ROADM (WSD9+WSM9)

The methods of calculating optical power in the preceding networking modes cover

all networking scenarios for WDM products. Mastering these methods greatly helps in

deployment and maintenance of WDM products.

P54

Thank You!

8-optical power calculation training

Documents

huawei optix

trademarks huawei

optix bws

hardware description

commissioning guide

signal flow1

wdm network

0d40m40 d40roadm