optical coupler

OPTICAL MULTIPLEXING AND OPTICAL AMPLIFIERS

Optical Coupler

The instructor:Hồ Đức Tâm Linh

Hoàng Chung Phạm Gia LươngMai Thị Quý Lệ

Trần Thị Kiều Oanh

Contents:I. THEORY

1. Concept2. Principle of Operation3. Parameter4. Types and fuction5. Construction6. Application7. Fused Biconical Taper – FBT

II. SIMULATION

1. OPTICAL COUPLER

• Couplers are one of the most common devices in fibre systems, use to split, combine and diverged signals within systems.

• α is coupling ration, with α = ½, coupler divided signal input into two equal parts at the output. Coupler in this case is called coupler 3 dB.

1. OPTICAL COUPLER

• Bidirectional Couplers carry light in either direction.

• Directional Coupler carry light only direction.

• Passtive couplers is device allocate signals without change optical signal to electric signal.• Active couplers is electric device, can split or join electric signal.

2. PRINCIPLE OF OPERATION

• Light “couples” from one wavelength to the otherThe propagation mode of the combined waveguide• Electric fields outputs (Eo1 , Eo2), inputs (Ei1 , Ei2):

2. PRINCIPLE OF OPERATION

• When used only one active input:

• For a 3dB coupler the coupling length must be chosen to satisfy:

3. PARAMETER

• Excess Loss.

• Insertion Loss.

• Coupling Ratio.

3. PARAMETER

• Uniformity.

• Polariation-dependent Loss. Loss < 0.15dB.

• Directivity.

• Near – end Crosstalk

3. PARAMETER

• Return Loss

• Isolator.

4. OPTICAL COUPLER TYPES AND FUCTION

• Y Coupler simply divides the signal into two outputs.

• T Coupler fuctions the same as Y coupler, connect multiple terminals on a network.

Three port fibre Splitter:


Three port fibre Combiner: use to combiner signals from two input to single output.


Tree Coupler: - One or two inputs and split it into multiple outputs and

backward. - Tree couplers have been extensively used to split and

mix optical signal in CATV, LANs and all other kinds of optical comunication systems.


Four port fibre Coupler or X Coupler, use to split and join signal, also know is Diverged Coupler.

• Star Fibre Coupler: mixing optical signals from all inputs and then distribute them among all outputs.



Comphare T Coupler and Star Coupler:

5. CONSTRUCTION OF COUPLER

Fused coupler: The fibers are brought togetherand are then fused just like in a fusion splicer asseen in figure:


• A fused star coupler is made in a similar way


Mixing rod coupler: In mixing rod, the incoming light spreads out until it occupies the whole diameter of the fiber. And come out each receive some of the light.


Variable Coupler: A vernier adjustment allows precise positioning of the incoming fiber so that the light can be split accurately between the two output fibers to provide any required splitting ratio.

• Perform split/join optical signals .

• A star coupler nxn made by combining 3 dB coupler.

6. COUPLE APPLICATION

• Tap off a small portion of the light stream for monitoring purposes : α close to 1(0.90 – 0.95)

• Building blocks:ModulatorSwitchesFiltersMultiplexers/ demultiplexers



Amplifiers EDFA use to Coupler

Ampifiers RAMAN use to coupler


Internal struction of a 4 Channel WDM MUX and DEMUX

7. FUSED BICONICAL TAPER

• FBT method is the most common way of manufacturing coupler.• An optical fiber coupler is a device that distributes light from a main fiber into two or more fibers.

• Methods of fabricating:


Fibre twisted, then spot fused under tension to form an elongated “biconical taper structure”.

Features of FBT: low insertion loss low polarization dependent loss high return loss environmentally stable


Applications monitoring testing high speed systems


SUMMARY

• Couplers are one of the most common devices in fibre systems, use to split, combine and diverged signals within systems.

• There are two types Tree and Star Coupler.• Coupler has an important role in optical

system.

optical coupler

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