coupler
Post on 26-Oct-2015
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OPTICAL MULTIPLEXING AND OPTICAL AMPLIFIERS
The Coupler
The instructor:Hồ Đức Tâm Linh
Hoàng Chung Phạm Gia LươngMai Thị Quý Lệ
Trần Thị Kiều Oanh
Contents:
1. Concept2. Classification3. Application4. Parameter5. Principle of Operation6. Fused Biconical Taper - FBT
1. OPTICAL COUPLER
• An optical coupler is a passive optical component that able to combine or slip stransmission data from optical fiber.
• Couplers are bi-directional, they can carry light in either direction.
2. OPTICAL COUPLER TYPES
• Y Coupler (Tap Coupler).
- Coupler simply divides the signal
into two outputs.• T Coupler
- Fuctions the same as Y coupler.
- Connect multiple terminals on a network.
2. OPTICAL COUPLER TYPES
• Star Coupler. Directional Star Coupler
Mixing optical signals from all inputs and then distribute them among all outputs.
Non-directional Star Coupler
It takes inputs from all fibers and then distribute them among all fibers, both input and output.
Directional star coupler Non-directional star coupler
2. OPTICAL COUPLER TYPES
• 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.
2. OPTICAL COUPLER TYPES
• WDM Coupler.
- Split two different wavelengths into two outputs.
- WDM couplers are used to separate wavelengths transmitted for different through the same fiber.
• The power from each input is split equally among all the inputs.
• Tap off a small portion of the light stream for monitoring purposes :… close to 1(0.90 – 0.95)
• Building blocks:ModulatorSwitchesFiltersMultiplexers/ demultiplexers
3.Coupler Application
4. PARAMETER
• Uniformity.
• Polariation-dependent Loss.
Loss < 0.15dB.
• Directivity.
• Near – end Crosstalk
5. Principle of Operation
• Light “couples” from one wavelength to the otherThe propagation mode of the combined waveguide• Electric fields outputs (E01 , E02), inputs (E11 , E12):
• When used only one active input:
5. Principle of Operation
• For a 3dB coupler the coupling length must be chosen to satisfy:
6. Fused Biconical Taper
• FBT method is the most common way of manufacturing coupler.
• Fibre twisted, then spot fused under tension to form an elongated “biconical taper structure”.
• For multimode fibre higher order modes (rays with smaller refraction angles)
• Become unguided, leaving the core of Fibre A and coupling into fibre B.
6. Fused Biconical Taper
FBT Multimode Operation
• Process happens because in the tapered section the core diameters are reduced.
• Thus some power from port 1 is transferred gradually over the taper to port 3
• The amount of power is a function of the taper length and the degree of coupling
6. Fused Biconical Taper
FBT Multimode Operation
6. Fused Biconical Taper
• FBT Singlemode Operation
•In the case of monomode operation there is a complex coherent interaction between the fibres.•Leads to a periodic variation in the splitting ratio with taper length and with wavelength as shown below.•Thus singlemode FBT couplers are naturally wavelength specific.
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