high capacity optical fiber

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HIGH CAPACITY OPTICAL NETWORKSPRE-DISSERTATION

Submitted in partial fulfillment of the

requirement for the award of the

Degree of

MASTER OF TECHNOLOGY

IN

(Electronic and Communication Engineering)

By

Anshul

Under the Guidance of

Project Supervisor

Mr.Gurpartap Singh

Lovely School of Science and Technology

Lovely Professional University

Punjab

April 2013


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CERTIFICATE

This is to certify that the Pre Dissertation titled High Capacity Optical Networks that is being

submitted by Anshul is in partial fulfillment of the requirements for the award of MASTER OF

TECHNOLOGY DEGREE, is a record of bonafide work done under my /our guidance. The contents of

this Thesis, in full or in parts, have neither been taken from any other source nor have been submitted

to any other Institute or University for award of any degree or diploma and the same is certified.

Gurpartap Singh

Project Supervisor

Lovely Professional University

(Organization stamp)

Objective of the Thesis is satisfactory / unsatisfactory

ExaminerI Examiner II


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ACKNOWLEDGEMENT

Foremost, I would like to express my sincere gratitude to Mr. Gurpartap Singh who gave his heart

whelming full support in the completion of this pre-dissertation with his stimulating suggestions and

encouragement to go ahead in all the time of the pre-dissertation.

I would also like to thank ,Head of Electronics and Communication department,for providing with

adequate knowledge in carrying out the work more interestingly.

At last but not the least I would pay gratitude towards my parents and also like to thank God for thestrength for keeping me standing and providing hope that this pre-dissertation would be possible.


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CERTIFICATE

This is to certify that Ranjana. bearing Registration no. 10904258 has completed objective formulation

of thesis titled, High Capacity Optical Networks under my guidance and supervision. To the best

of my knowledge, the present work is the result of her original investigation and study. No part of the

thesis has ever been submitted for any other degree at any University.

Signature and Name of the Research Supervisor

Designation

SchoolLovely Professional University

Phagwara, Punjab.

Date :


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DECLARATION

I, Anshul, student of B.Tech-M.Tech. (Program name) under Department . of Electronics And

Communication Engneering Lovely Professional University, Punjab, hereby declare that all the

information furnished in this Pre Dissertation report is based on my own intensive research and is

genuine.

This thesis does not, to the best of my knowledge, contain part of my work which has been submitted

for the award of my degree either of this university or any other university without proper citation.

Date : 27 April 2013

ABSTRACT


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Optical performance monitoring is an important function for high capacity optical transmission system.

To meet the ever increasing demand for broadband services, future optical networks will have higher

data rates, higher spectral efficiency and more flexibility in light path assignment. we will summarizesome of the recent work that have carried out in this area. In particularly, PMD independent OSNR

monitoring of RZ-DQPSK signal and signed residue dispersion monitoring of CSRZ-DQPSK signal

using delay tap sampling and asymmetry ratio are presented. It presents the new design concepts toimplement advanced high-capacity avionics optical fiber information exchange networks (AOFIE-

networks). Very-high-speed medium access protocols are proposed to support multi-gigabit per second

data communications, and the considerations on network design are described to match the

requirements for aircraft applications. Optical time-division multiple access networks are shown to bevery efficient for on-board TV and audio distribution services, while an optical code-division multiple

access network is attractive to high-speed asynchronous packet data transfer. Since wavelength-division

multiple access (WDMA) has advantages of channel independence and protocol transparence, it makes

WDMA networks very suitable for real-time multiservice communications and on-board networkinterconnection. With the tremendous growth in the Internet and the use of multimedia services, the

demands for increased transmission capacity and switching/routing-node throughput for trunk

networks are increasing rapidly. In addition, networks must now accommodate a variety of services asindependently as possible. Optical network technology will play an important role in constructing cost-

effective transparent trunk networks. In this paper we briefly discuss the technologies needed to

implement optical networks: wavelength division multiplexing (WDM) to increasetransmission capacity, photonic transport to support high-capacity flexible networks, and photonic

switching to expand node capacities and functionality.

TABLE OF CONTENTS Page no.


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Chapter 1:Introduction. 10

1.1-Detection..... 11

1.2-Error Performance.12

1.3-Optical filter based Mitigation Group Delay Ripples.12

1.3.1-Determination of Statistical Multi Freq phase ripples..131.3.2-Simulation setup13

1.4-Statistical model.14

1.5-Optical Equalizer structure..14

1.5.1-Filter structure for PMD15

1.6-High capacity optical networking techniques..16

Chapter 2: Literature Survey..17

Chapter 3:Broadarea and problem formulation20

3.1-Receiver.. 203.2-Fiber cable type.21

3.3-Regenerate.. 22

4.References. 24

5. Biodata.. 25

LIST OF FIGURES


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Figure 1- NTEST fiber watch

Figure 2- Acable real trailer with conduit that can carry optical fiber

Figure 3-Single mode optical fiber in underground service pit


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LIST OF ABBREVIATIONS

OPM- Optical Performance Monitoring

NR-Optical Signal to Noise Ratio

CO-Chromatic Dispersion

OTN-Optical Transport Network

PMD- Polarization mode Dispersion

WDM-Wavelength Division Multiplexed

FBGs- Fiber Bragg Grating

MMC- Multi canonical Monte Carlo

GDR-Group Delay Ripple

NRZ-Non Return to Zero

RZ-Return to Zero


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CHAPTER:- 1 INTRODUCTION

Fiber optic communication is a method of transmitting information from one place to another bysending pulses of light through an optical fiber. The light forms an electromagnetic carrier wave that is

modulated to carry information. Advantages over electrical transmission ,optical fibers have largely

replaced copper wire communications in core networks in the developed world. The process ofcommunicating using fiber-optics involves the following basics steps:

Creating the optical signal involving the use of a transmitter ,relaying the signal along the fiber,

ensuring that the signal does not become too distorted or weak, receiving the optical signal ,and

converting it into an electrical signal .To meet the ever increasing demand for broadband widthservices, future optical networks will have higher data rates, higher spectral efficiency and more

flexibility in light path assignment. This means transmission system parameters for the links in the

network need to be controlled to be within a much tighter range in order to ensure proper operation of

the networks.

Optical performance monitoring(OPM) functions are essential for monitoring these parameters in order

that dynamic impairment compensation, efficient resources allocation and impairement aware routing

can be carried out to ensure the proper operation of the networks. Among the system parameters to bemonitored include signal wavelength ,optical signal to noise ratio(OSNR ), chromatic dispersion

(CO),polarization mode dispersion (PMD) and non linear. In backbone optical transport

networks(OTN),high capacity transmission technologies are essential to provide various broadband

services such as video-sharing, high definition video-on-demand, and network computing.

Network traffic demands are forecast to increase for the foreseeable future, with the challenge being tomeet the demand while maintaining or lowering network costs. Simply increasing capacity will not be

sufficient; overall bandwidth utilization also needs to improve. A combination of improvedtransport capacity through increased spectral efficiency and bit rate along with

better network utilization by integrating sub channel electrical grooming into the transmission system

will be required. Smarter ways to utilize optical capacity are key since transmission costs have been

decreasing slower than grooming and switching costs. Integrated transport and switching can improvethe efficiency of the client network using techniques such as port virtualization and transit traffic

reduction. The baseline for transport networks will be 100 Gb/s PM-QPSK using 50 GHz channel

spacing. Moving from a fixed DWDM channel arrangement to support flexible grid and super channels

will allow tighter channel (carrier) spacing and should increase capacity by 30 to 50 percent. For

shorter distances higher-order modulation such as 16-QAM can double network capacities.Advanced optical modulation formats have become a key ingredient to the design of modern

wavelength-division-multiplexed (WDM) optically routed networks. In this paper, we review thegeneration and detection of multi gigabit/second intensity- and phase-modulated formats and highlight

their resilience to key impairments found in optical networking, such as optical amplifier noise,

chromatic dispersion, polarization-mode dispersion, WDM crosstalk, concatenated optical filtering, andfiber nonlinearity. Coherent detection with digital signal processing enables the use of the multi-level

modulation format and polarization-division multiplexing(PDM), and thus dramatically increases the


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spectral efficiency. Since higher speed interfaces such as 400G Ethernet are expected, research Interest

is shifting to the long-haul transport of such higher speed client signal ,100-Tb/s-class total capacity is

required in next generation. Many optical networks have link rates of 2.5 Gigabits per second, andresearch teams are deploying 10 and 40 G bit/sec optical links in experimental network test beds (e.g.,

the Internet2 Abilene backbone, and the NSFs Tera Grid) [Dr00]. If the optical links are conditioned

to carry multiple channels via wavelength division multiplexing, then a networks capacity can exceedtens of Peta bits per second. The Global Grid Forum has identified basic requirements for applicationsand services that use optical network resources; these include: (1) a scalable, flexible, and rapidly

reconfigurable optical network infrastructure; (2) ultra high bandwidth on demand between arbitrary

endpoints; and (3) user/application provisioning and control of bandwidth with sub-wavelengthgranularity .Provisionable optical networks have been identified by the U.S. National Science

Foundation and various Federal agencies as an essential and critical part of the Nations information

infrastructure. Unfortunately, large-scale, ultra high capacity optical networks cannot be realistically

modeled and analyzed using todays methods and tools. A new approach is required to provide insightinto how applications and services that rapidly provision and release network resources might behave in

these networks.

Ultra high capacity optical networks that are able to provide bandwidth on demand cannot be modeledwith high fidelity using todays methods and tools. Discrete event and hybrid simulators, and (near)

real time network emulators capable of processing several hundred thousand packets per second

cannot cope with aggregate traffic volumes four or five orders of magnitude .In high-capacity metronetworks, fiber Bragg gratings (FBGs) offer a potentially cost-effective solution for compensation of

chromatic dispersion (CD). However, FBGs suffer from stochastic variations of their group delay, the

so-called group delay ripple (GDR). We propose a novel statistical model to describe the effects of

stochastic variations of GDR. The statistical properties of our model are verified by comparison tomeasurement data and Monte Carlo simulations as well as Multi canonical Monte Carlo (MMC)

simulations. Results indicate that without further measures to counteract the GDR distortions, very

large penalties (>; 10 dB) for the optical signal-to-noise ratio (OSNR) occur frequently at a bit rate of112 G bit/s. Thus, we investigated the performance of short and cost-effective optical finite and infinite

impulse response equalizer structures to mitigate the GDR distortions and to enhance the signal quality.

With the use of optical equalizers (which can be realized as planar light wave circuits) we were able toreduce the mean OSNR penalty due to the GDR to less than 0.1 dB. We also demonstrate that the same

filter structures can efficiently be used to mitigate all-order PMD distortions as well.

1.1 DetectionEfficient detection of FDM signals depends on the properties of the covariance matrix M (i.e. the Gram

matrix) that appears in the linear statistical model . The Gram matrix is positive semi definite upper

triangular, so its eigen values equate to its diagonal elements. In the OFDM case the ortho normal base

coincides with the FDM carriers and consequently M =IN. On the other hand, in the FDM case, with

decreasing carrier spacing and/or increasing number of carriers N, the Gram matrix eigen valuesdecrease rapidly and M tends to become singular. Next, the well known iterative steps of SD based onthe previous formula are applied. The improvement in the condition number of matrix D, due to the


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regularization process, is depicted . We need to underline the fact that the GSD based FDM detection

can be easily expanded for higher level QAM schemes since non-constant modulus M-QAM symbols

(M > 4) can be expressed as linear combinations of 4-QAM symbols .Finally, in our implementation ofthe GSD, we followed the Schnorr Euchner (SE) enumeration strategy, as applied to MIMO systems .

1.2 Error Performance

Error rate simulations were performed for different values of fT and different noise levels. It showsthat with Eb/N0 = 8 dB the system approximates the BER of an OFDM scheme if the frequency

separation between the FDM carriers is reduced up to 0.7 the FDM system with up to 32 carriers and

25% bandwidth saving (relative to an equivalent OFDM system) approximates the OFDM performance

for between 5 and 8 dB. Finally, we show the applicability of the method through detailed systemmodeling and simulations. In particular, it is shown that for practical Eb/N0 values the proposed

receiver could afford the computational cost of the detection of a 4-QAM IMGS FDM signal of N = 32carriers with up to 25% bandwidth saving relative to a standard OFDM signal.

1.3 Optical Filter Based Mitigation Group Delay Ripple

In high-capacity metro networks, fiber Bragg gratings (FBGs) offer a potentially cost-effective

solution for compensation of chromatic dispersion (CD). However, FBGs suffer from stochasticvariations of their group delay, the so-called group delay ripple (GDR). We propose a novel statistical

model to describe the effects of stochastic variations of GDR. The statistical properties of our modelare verified by comparison to measurement data and Monte Carlo simulations as well as Multi

canonical Monte Carlo (MMC) simulations. Results indicate that without further measures to

counteract the GDR distortions, very large penalties (>; 10 dB) for the optical signal-to-noise ratio

(OSNR) occur frequently at a bit rate of 112 G bit/s. Thus, we investigated the performance of shortand cost-effective optical finite and infinite impulse response equalizer structures to mitigate the GDR

distortions and to enhance the signal quality. With the use of optical equalizers (which can be realized

as planar light wave circuits) we were able to reduce the mean OSNR penalty due to the GDR to less

than 0.1 dB. We also demonstrate that the same filter structures can efficiently be used to mitigate all-

order PMD distortions as well. The distortion caused by physical impairments which accur along thetransmission link such as chromatic dispersion (CD) and polarization mode dispersion (PMD) are

more severe at higher bitrates and may causes a significant decrease in signal quality. For high valuesof uncompensated CD or P M D ,it may even be impossible to detect an eye opening at the receiver

without any further measures, Metro networks, however are very cost-sensitive application area. a

lower cost solution which does not necessarily involve the deployment of DSP and POLMUX-QPSKwould be preferred. The FBGs suffer from so-called group delay ripples .GRD is created due to

inherent statistical deviations from the ideal linear dispersion gradient which may lead to inter symbol


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interference(ISI) and thus potential signal degradation. The maximum spectral bandwidth for each

channel for these applications is predetermined by the 50GHz ITU grid

1.3.1 Determination of statistical multi frequency phase ripples and single frequency ripples

The multi frequency ripples are taken from a group delay measurement of a commercial DCFBG. The

phase ripple characteristics are extracted by subtracting the linear part from the measured group delay

characteristic over wavelength for one channel. The remaining GDR, which has a peak-to-peak rippleamplitude of 19 p s maximum, is integrated over the wavelength. To randomize the ripple influence,

this characteristic is shifted cyclically with respect to the carrier frequency of the laser signal. With this

method, a set of 100 different FBGs is modeled. These 100 FBGs are composed randomly together in1000 different multi span links, each consisting of up to 20 FBGs. The phase ripple of one FBGrepresented as the phase response b(f) can be separated into different frequency components by Fourier

series expansion These three parameters determine the influence of the ripple on the signal. The

sinusoidal phase distortion leads to pre and post curser echoes with temporal distance of n/frip to themain signal pulse and weighted by the Bessel function of the n-th order J n as the impulse response of

a single frequency ripple device shows.

1.3.2 Simulation setup

The simulation setup with a data rate of 11 G b/s is shown in Fig. 1. The considered modulation

formats are amplitude shift keying (ASK), differential phase shift keying (DPSK), and differential quad

rature phase shift keying with non-return-to-zero (NRZ) and return-to-zero (RZ) pulse shapes,respectively, and optical duobinary (ODB). For the differential formats, balanced detection is applied.

To focus on the influence of the ripples, we consider full compensation of dispersion and linear fiber.

The receiver consists of a 100 GHz Gaussian optical filter and a photo diode, followed by an electrical

3rd order Butterworth filter with bandwidth 0.7x symbol rate for NRZ and 1.1x symbol rate for RZ.

The received signal is evaluated after every second FBG. Since OSNR estimation for the enormousnumber of received signal wave forms (1000x10 for each modulation format) would take too much

time, the eye opening penalty (EOP) as the ratio of the maximum opening of the disturbed eye and the

eye without ripple influences is measured .For single frequency ripple simulations the optical and theelectrical filter are left out and only one FBG with sinusoidal ripples determined by g, frip and 0 is

investigated.


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1.4 Statistical Model

When performing the fourier analysis of the experimentally obtained data, one can sort the values forthe fourier coefficients of the GDR amplitudes in each distinct ripple period and all channels of the

FBGs. The resulting distribution for othe GDR amplitudes can be approximately by using a log normal

distribution.The lognormal distribution has two degrees of freedom with being the expectations valueand the individual fourier coefficient. The iterative Bayesian algorithm is applied to computer-

generated ideal data and to experimental phantom imaging data containing Poisson noise. Improvement

in image processing with the Bayesian algorithm is demonstrated by comparing the processed images

and the convergence performances of objective evaluation test functions obtained by using theBayesian algorithm with those obtained by using the standard maximum-likelihood algorithm. A

Bayesian analysis considering both the a priori source distribution probabilistic models and the Poisson

statistics of photon detection fluctuations is studied. The Bayesian solution determined by a system ofequations that maximizes the a posteriori probability, given the measured data, is presented. A

Bayesian image-processing algorithm that obtains the solution iteratively is derived by using an

expectation-maximization technique.

1.5 Optical Equalizer Structure and Determination of Equalizer Coefficients

The transversal FIR filter functional diagram is depicted in Fig 1. (left). In order to mitigate PMD-

related distortions, a very simple approach would be to implement two parallel filter structures: Eachequalizer structure has its own set of coefficients and can be adjusted independently while the input and

output signals are split and, respectively, combined using a polarization beam splitter (PBS) . In this

contribution we also implemented a so called butterfly structure as depicted in consisting of four FIRequalizer subsets which can be adjusted independently from each other. In a system with direct

detection, the conventional approach of using (e.g.) the constant modulus algorithm (CMA) and/or a

decision-directed algorithm cannot be used since the complex signal and thus the phase information is

not known at the receiver. However, the tap coefficients can be found using a numerical optimizer.Previous studies have shown, that using a training sequence (512 bits) to guide the numerical

optimizer to a solution for the set of tap coefficients achieves very good results. In this case, the least

mean squares error which is composed of the difference of the detected signal power and the known

training sequence is used as a feedback criterion. In our studies, we have used a MATLAB TMimplementation of the trust region algorithm and a Leven berg-Marquardt (LM) algorithm to solve the

(nonlinear) optimization problem. The equalizers can be realized as planar light wave circuit devices

(PLC) which are composed of Si ON . They can also be used to equalize group delay ripples (GDR)due to deviations from an ideal dispersion compensation scheme as has been shown in . In contrast to


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electrical equalization, which has been intensively studied , optical equalization has received

comparatively little attention . We have carried out extensive numerical simulations to compare two

alternative strategies to realize an optical PMD equalizer and we found that the occurring maximumand mean penalties can be significantly reduced, when optical equalization is implemented. We also

outline how the adaptation process for the filter coefficients can be realized.

1.5.1 Filter Structures for PMD Equalization

Polarization mode dispersion (PMD) in a dual-pole optical communications network is compensatedfor using an adaptive PMD equalizer. The PMD equalizer may include a number of substantially

identical filter modules that provide partial outputs which may be combined to form a PMD

compensated output. A constant modulus algorithm (CMA)-based equalizer may track PMD acrossboth poles and generates an error signal. The CMA-based equalizer includes a filter bank, and uses an

update algorithm and tap/output adjustments based on a difference between combined tap energies and

an index, and feedback from a forward error correction code frame synchronizer .An apparatus for

adaptive equalization of polarization mode dispersion in an optical signal, comprising: an inputconfigured to receive multiple input channels corresponding to digitized versions of in-phase and

quadrature channels of horizontal and vertical polarity optical signals; a plurality of substantially

identical finite impulse response (FIR) filter modules, configured to receive the input channels, receivefilter tap error updates, adjust FIR filter tap values based on the received tap error updates, partially

filter one or more of the input channels based on the adjusted FIR filter tap values, and output one or

more partially filtered input channels; and an error calculation and output generation module configured

to receive the partially filtered input channels from the FIR filter modules, combine the partially filteredinput channels, output a polarization mode dispersion compensated version of each channel of the

digitized. .

A method for adaptive equalization of polarization mode dispersion in an optical signal, the method

comprising: receiving multiple input channels corresponding to digitized versions of in-phase and

quadrature channels of horizontal and vertical polarity optical signals; partially filtering one or more ofthe input channels at a plurality of substantially identical FIR filter modules, each of the plurality of

FIR filter modules including a portion of the filter taps for one or more FIR filters; receiving partially

filtered input channels at an error calculation and output generation module; calculating, at the error

calculation and output generation module, tap error updates for each of the FIR filter modules;outputting, from the error calculation and output generation module, the tap error updates to the

plurality of FIR filter modules; and outputting, from the error calculation and output generation module.


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A method of polarization mode dispersion compensation may include receiving a digitized version of

an optical signal, and utilizing a constant modulus algorithm in an adaptive equalizer to compensate for

the effects of polarization mode dispersion.

1.6 High capacity optical networking technologies

With the tremendous growth in the Internet and the use of multimedia services, the demands for

increased transmission capacity and switching/routing-node throughput for trunk networks are

increasing rapidly. In addition, networks must now accommodate a variety of services as independentlyas possible. Optical network technology will play an important role in constructing cost-effective

transparent trunk networks. In this paper we briefly discuss the technologies needed to implement

optical networks: wavelength division multiplexing (WDM) to increase transmission capacity, photonictransport to support high-capacity flexible networks, and photonic switching to expand node capacities

and functionality. The Internet has produced higher demands for broadband services, leading to

extensive growth in Internet Protocol (IP) data traffic and putting pressure on service providers to

upgrade their existing networks. Fibre -To-The-Home (FTTH) for broadband access applications maybe considered as an effective solution for higher capacity access networks as optical fiber in

telecommunications have huge capacity, small size, light in weight, very high bandwidth, and

immunity to electromagnetic interference, etc. The PON based technologies are somewhat new forIndian telecom environment and will grow extensively in due course. The Gigabit passive optical

network (GPON) and Ethernet Passive Optical Network (EPON) is considered to be a very attractive

solution for implementing FTTX (Tiber To The Home/Business/Curb/Premises etc). The question will

rise that what will be the next fiber access technology? Two technologies stand out in the industrywould be 10G PON as a continuation of GPON and/or EPON & WDM-PON.


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CHAPTER 2 Literature survey

The paper reviews the recent technical challenges of digital-signal-processing (DSP)-aided high-speedchannel for future high-capacity Optical Transport Network (OTN) with the channel data rate beyond

100Gbit/s. In high-capacity metro networks, fiber Bragg gratings (FBGs) offer a potentially cost-

effective solution for compensation of chromatic dispersion (CD). However, FBGs suffer fromstochastic variations of their group delay, the so-called group delay ripple (GDR). We propose a novelstatistical model to describe the effects of stochastic variations of GDR. The statistical properties of our

model are verified by comparison to measurement data and Monte Carlo simulations as well as Multi

canonical Monte Carlo (MMC) simulations. Results indicate that without further measures tocounteract the GDR distortions, very large penalties (>; 10 dB) for the optical signal-to-noise ratio

(OSNR) occur frequently at a bit rate of 112 G bit/s. Thus, we investigated the performance of short

and cost-effective optical finite and infinite impulse response equalizer structures to mitigate the GDR

distortions and to enhance the signal quality. With the use of optical equalizers (which can be realizedas planar light wave circuits) we were able to reduce the mean OSNR penalty due to the GDR to less

than 0.1 dB. We also demonstrate that the same filter structures can efficiently be used to mitigate all-

order PMD distortions as well. With the tremendous growth in the Internet and the use of multimediaservices, the demands for increased transmission capacity and switching/routing-node throughput for

trunk networks are increasing rapidly. In addition, networks must now accommodate a variety of

services as independently as possible. Optical network technology will play an important role in

constructing cost-effective transparent trunk networks. In this paper we briefly discuss the technologiesneeded to implement optical networks: wavelength division multiplexing (WDM) to increase

transmission capacity, photonic transport to support high-capacity flexible networks, and photonic

switching to expand node capacities and functionality .

A collection of slides from the author's conference presentation is given. (Fiber- Wireless) is the

combination of optical networking technology and wireless networks. Wi fi networks are very costeffective, gives high capacity bandwidth and the best solution to full fill the demand of bandwidth

hungry applications like quad play, online gaming etc. Our goal is to reduce the delays in Fi-

Wi networks. In this paper we proposed most nearest most used routing algorithm (MNMU-RA) toovercome the delays in wireless (front end of Fi-Wi). Our algorithm shows the significant improvement

in Delay and throughput of the network. Telecommunication networks call for novel energy-efficient

design and management schemes as a result of the increasing contribution of the ICT sector to

electricity consumption and greenhouse gas emissions. Access networks, being one of the significantcontributors in the last mile, require power saving protocols and architectures. As one of the emerging

access network solutions, convergence of PONs and wireless access networks, also named as Fi Wi,

offer to combine the robustness and high capacity of optical networks with the mobility and ubiquity of

wireless networks. In this article, we present an overview and a brief comparison of energy-efficientprotocols and design approaches in Fi Wi networks. We further propose an energy-efficient bandwidth

allocation mechanism in FiWi networks that adopts an optical burst switching (OBS)-like report

generation mechanism in LREPON. Through simulations, we show that the proposed scheme leads tosignificant energy savings in the long-reach FiWi network while overcoming the delay penalty of the


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ONU-BS sleep modes. This article presents ACCORDANCE, a novel optical access

network architecture based on OFDMA technology and applied on a PON topology. In compliance

with next generation optical access requirements, this architecture aims to outperform existing PONsolutions in terms of total capacity, bandwidth allocation flexibility, number of users,

and network reach. Moreover, it provides the opportunity for convergence with wireless technologies

and a smooth migration path from legacy access solutions like TDMA-PONs and DSL.

The last mile solutions for high-speed high-capacity optical networks capable of securely supporting

large number of simultaneous users by minimal hardware requirements are needed but it seems that any

such solutions are still far away. Access networks based only on a wavelength-division multiplexing

(WDM), optical time division multiplexing (OTDM) or optical code-division multiplexing (OCDM)schemes can't do it as the standalone systems. Here we present a proof-of-concept field demonstration

of the implementation of an incoherent OCDMA over OTDMA system (iOCDM-OTDM) using a

17km long bidirectional fiber link installed between the Strathclyde and Glasgow Universities. Theperformed system performance analyses include system scalability calculations and a system reach

under the influence of transmission link physical impairments. optical transmission technologies are

able to support 400Gbps over a single optical channel. However, this capacity cannot tit in the current

fixed frequency grid optical spectrum. On the other hand, high rate optical channels have to co-existwith different ranges of line rates in order to serve heterogeneous bandwidth requests from variety of

internet applications. Today's fixed rate and rigid frequency grid optical transmission systems cause

over provisioning, where usually more spectral resources are provided than necessary. Recently, theconcept of elastic optical network has been proposed in order to reduce this waste of resources.

In networks with such feature enabled, modulation parameters and central frequencies are not fixed and

the resources can be allocated with a fine granularity, in contrast to the traditional WDM networks.

This flexibility makes it possible to adapt to the granularity of the requested bandwidth without overprovisioning. However, this heterogeneous bandwidth allocation may on the other hand result in

fragmentation of spectral resources under dynamic traffic.

We present a scalable high fan-out optical network (HF-PON) architecture that supports 450+

simultaneous users and an aggregate downstream bandwidth of 100Gb/s using quadrature amplitude

modulation, coherent optical orthogonal frequency division multiplexing (QAM-OFDM) sub-carrier

modulation scheme. Presented architecture is best suited for high-capacity bandwidth hungryapplications such as in-flight entertainment networks and can be deployed in small and geographically

confined areas. Simulation results show that HF-PON is able to provide up to ~195Mb/s to each user

with BER kept under the FEC threshold. The high capacity transport infrastructure that underpins

today's Internet utilizes optical wavelengths both to provide high capacity transmission by means ofmultiplexing many wavelengths, each carrying as much as 100 G b/s on a single wavelength, but also

to provide coarse networking flexibility by dynamically adding, dropping, and routing wavelength

channels. Viewed initially by many as little more than a dreamlike vision, these wavelengthswitched networks have now been deployed in both metro and long-haul networks around the globe to


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provide flexible, cost-effective high bandwidth connectivity to meet the explosive growth in demand of

very broadband wire line and wireless services, especially video. The success of these networks, as

signified by their ubiquitous deployment, is a result of a fortuitous combination of three factors: Anew network vision that, with the help of optical switching elements, leverages the advantage

of optical amplifiers at the network as well as the transmission systems level; Popularization of video-

centric handheld devices including smart phones and computer tablets has led to a sharp increase in thedemand for wired and wireless data capacity and coverage towards the edge of moderncommunication networks. Since these devices are operated mostly from inside buildings, in-building

coverage and capacity have also become critical components of wireless networks. But poor

propagation of wireless signals inside buildings leads to significant performance degradation ofwireless systems in terms of both coverage and capacity. As a result, a high density of antennas is

needed to provide the required performance. Due to its inherent large bandwidth, optical fiber is ideally

suited to provide flexible backbone infrastructure of high-capacity wireless networks. By employing

analog radio-over-fiber signal transmission techniques, highly transparent fiber-wireless networks,which are ideal for multi-standard wireless system operation can be realized. We have demonstrated

multiple simple techniques that may be used solve many technical challenges faced when analog signal

transport is employed. Using simple and practical solutions, we have experimentally demonstratedultra high-capacity radio-over-fiber systems operating at >; 30 G b/s.

Optical networks continue to play an essential role in scaling network capacity at a dramatically

reduced unit bandwidth cost, and the next generation of technology will continue this trend.Automation of optical networks has reduced operations costs and enabled customer control of high-

bandwidth services. We anticipate application-driven control of optical networks to appear in the near

future. This paper looks to emerging technologies, both at the physical layer and network control layer,

with a goal of assessing their impact on next-generation optical network architectures. We look forwardto orders of magnitude improvement both to the capacity and complexity of intelligent optical networks.

we provide a historical perspective on the evolution of optical networks, with some emphasis on the

Defense Advanced Research Projects Agency (DARPA)-funded Multiple Wavelength OpticalNetwork (MONET) program, which demonstrated the technical feasibility of wavelength-division

multiplexing (WDM) optical networks. The last mile solutions for high-speed high-capacity optical

networks capable of securely supporting large number of simultaneous users by minimal hardwarerequirements are needed but it seems that any such solutions are still far away. Access networks based

only on a wavelength-division multiplexing (WDM), optical time division multiplexing (OTDM)

or optical code-division multiplexing (OCDM) schemes can't do it as the standalone systems. Here we

present a proof-of-concept field demonstration of the implementation of an incoherent OCDMA overOTDMA system (iO CDM-OTDM) using a 17km long bidirectional fiber link installed between the

Strathclyde and Glasgow Universities. The performed system performance analyses include system

scalability calculations and a system reach under the influence of transmission link physical

impairments.


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CHAPTER 3 Broad Area and Problem Formulation

Many network operations managers are well acquainted with the network monitoring tools designed to

monitor the status of applications on their networks; however, few monitor the health of their opticalnetwork, yet this can often be the cause of network performance degradation. Reactive networktroubleshooting is not sufficient as this approach may require too much time to identify and isolate

problems; thus damaging an organization's reputation, diminishing customer service expectations and

ultimately reducing an organization's revenue stream in the time needed to make necessary repairs.Designed for full service, emerging and next generation public and private networks, FiberWatch is the

first Remote Fiber Testing System that allows the network operations manager to proactively monitor

the fiber optic network through use of Domains, thus enabling delivery of the highest level of QoS and

ensuring network security aand reliability to the greatest degree.

3.1 Receivers

The main component of an optical receiver is a photo detector, which converts light into electricity

using the photoelectric effect. The primary photo detectors for telecommunications are made

from Indium gallium arsenide The photo detector is typically a semiconductor-based photodiode.

Several types of photodiodes include p-n photodiodes, p-i-n photodiodes, and avalanche photodiodes.Metal-semiconductor-metal (MSM) photo detectors are also used due to their suitability for circuit

integration in regenerators and wavelength-division multiplexers. Optical-electrical converters are

typically coupled with a trans impedance amplifier and a limiting amplifier to produce a digital signal

in the electrical domain from the incoming optical signal, which may be attenuated and distorted while

passing through the channel. Further signal processing such as clock recovery from data (CDR)

performed by a phase-locked loop may also be applied before the data is passed on.


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3.2 Fiber cable types

A cable reel trailer with conduit that can carry optical fiber.

Single-mode optical fiber in an underground service pit

An optical fiber consists of a core, cladding, and a buffer (a protective outer coating), in which the

cladding guides the light along the core by using the method of total internal reflection. The core and

the cladding (which has a lower-refractive-index) are usually made of high-quality silica glass,

although they can both be made of plastic as well. Connecting two optical fibers is done by fusion

splicing or mechanical splicing and requires special skills and interconnection technology due to the

microscopic precision required to align the fiber cores.

Two main types of optical fiber used in optic communications include multi-mode optical

fibers and single-mode optical fibers. A multi-mode optical fiber has a larger core ( 50 micrometers),

allowing less precise, cheaper transmitters and receivers to connect to it as well as cheaper connectors.

However, a multi-mode fiber introduces multimode distortion, which often limits the bandwidth and

length of the link. Furthermore, because of its higherdopant content, multi-mode fibers are usually

expensive and exhibit higher attenuation. The core of a single-mode fiber is smaller (


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and requires more expensive components and interconnection methods, but allows much longer,

higher-performance links.

3.3 Regeneration

When a communications link must span a larger distance than existing fiber-optic technology is capable

of, the signal must be regeneratedat intermediate points in the link by repeaters. Repeaters add

substantial cost to a communication system, and so system designers attempt to minimize their use.

Recent advances in fiber and optical communications technology have reduced signal degradation so

far that regeneration of the optical signal is only needed over distances of hundreds of kilo meters. This

has greatly reduced the cost of optical networking, particularly over undersea spans where the cost and

reliability of repeaters is one of the key factors determining the performance of the whole cable system.

The main advances contributing to these performance improvements are dispersion management, which

seeks to balance the effects of dispersion against non-linearity; and solutions, which use nonlinear

effects in the fiber to enable dispersion-free propagation over long distances.

The design of future all-optical networks relies on the knowledge of the physical layer transportproperties. In this thesis, we focus on two types of system impairments: those induced by the non-ideal

transfer functions of optical filters to be found in network elements such as optical add-drop

multiplexers (OADM) and optical cross-connects (OXC), as well as those due to the interaction ofgroup-velocity dispersion, optical fibre non-linearities and accumulation of amplifier noise in the

transmission path. The dispersion of fibre optics components is shown to limit their cascadability.

Dispersion measurement techniques are first reviewed, and the limitations of the commonly usedphase-shift technique is discussed. Additionally, an alternative method which enables the direct

determination of small dispersion values in the pass-band of optical filters is proposed. Available

optical filter technologies are compared with respect to their dispersive properties. The cascadability of

fibre gratings is investigated numerically and experimentally. The conventional Gaussian apodisationprofile is shown to result in unwanted dispersion in the pass-band, which will limit its cascadability to

less than five devices when a channel spacing of 50 GHz is used at 10 G bit/s. The use of narrow

bandwidth modulation formats such as optical duo binary is suggested in order to improve the detuning

tolerance of Gaussian apodised gratings. Alternatively, novel asymmetric apodisation profiles withmultiple phase-shifts can be designed to provide reduced dispersion in the pass-band. Large detuning

tolerances are demonstrated experimentally for a variety of modulation formats. A numerical

optimisation of pass-band flattened phased array (PHASAR) multiplexers is performed for use in highspectral efficiency metropolitan area networks at 40 G bit/s. Even if conventional PHASARs are

theoretically dispersion-less devices, the pass-band flattening process is shown to induce unwanted

dispersion, which will ultimately limit the device cascadability. A PHASAR based on a parabolic horninput coupler is found to be the most promising design in order to maximise the spectral efficiency in a


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four add-drop node ring network. The concept of "normalised transmission sections" is introduced in

order to ease the dimensioning of transparent domains in future all-optical networks. Normalised

sections based on standard single mode fibre (SMF) and dispersion compensating fibre (DCF) areoptimised numerically with respect to the positioning of the DCF, the degree of compensation and the

input powers to the two fibre types. Experimental validations are performed for 10 Gbit/s non return-to-

zero (NRZ) and chirped return to-zero (CRZ) modulation over 80 km pre-compensated spans. Passivepre distortion at the transmitter is shown to significantly improve the reach of the systems. Based on theexperimental results, transparent domains with a diameter of the order of 1000 km can be realised, thus

demonstrating the applicability of the optimisation method to the design of large area networks.

Wavelength division multiplexing (WDM) systems not only require compensation of the dispersion ofthe transmission fibre, but also of its dispersion slope. The effectiveness of early slope compensating

DCFs for broadband compensation of SMF is demonstrated experimentally for 10 Gbit/s NRZ

modulation. In particular, transmission in the L-band is achieved over more than 1000 km using a

dispersion map optimised for the C-band, removing the need for separate band compensation. NovelDCFs enabling for the cabled compensation of the dispersion and dispersion slope of SMF (the so-

called inverse dispersion fibres, IDFn, where n is the SMF to DCF length ratio), are compared

numerically. For NRZ modulation at 10 Gbit/s, IDF1 is found to maximise the transmission distanceover 50 km spans for single channel, while being prone to cross-phase modulation in WDM systems

where IDF2 or 3 should be preferred. The benefit of using short return-to-zero (RZ) pulses over

conventional NRZ modulation in a SMF+IDF1 link is highlighted. Short pulses disperse faster in the

transmission fibre, which is in turn beneficial in terms of optical signal-to-noise ratio, resulting in atwofold increase in transmission distance over NRZ for a 3 dB power penalty criterion.


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Refrences

[1] S.J.Savory,Digital filters for coherent optical receivers.Opt.Exp,vol.16,no.2,pp.804-817,2008.

[2]www.opticsinfobase.org Optics and Photonics News Volume 14 Issue 9

by M Oikawa - 2003

[3] www4.ncsu.edu/~hp/Bragg.pdf

[4] xa.yimg.com/kq/groups/24534646/885915896/name/paper11.pdf

[5] www.amazon.com/University-Nebraska...high-capacity.../B000Y76JKE

[6]www.kochi-tech.ac.jp/kut_E/graduate/image/iwashita.pdf

[7]I.Kaminov,optitcal fiber and tecommunication IV B.New York:Academic,2002,pp.658-695

[8]D.W.Marquardt,An algorithm for least-square estimation of non linear parameters,SIAMJ.Appl.Math,vol.11,pp.431-441,1963
http://www.opticsinfobase.org/opn/http://www.opticsinfobase.org/opn/browse.cfm?journal=13&strVol=14http://www.opticsinfobase.org/opn/issue.cfm?volume=14&issue=9http://www.opticsinfobase.org/opn/issue.cfm?volume=14&issue=9http://www.opticsinfobase.org/opn/browse.cfm?journal=13&strVol=14http://www.opticsinfobase.org/opn/

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