FBT coupler

1. Definition

  Coupler is a device that can couple and redistribute optical signals in the coupling zone of a special structure during transmission.

2. Classification

Features：Splitter

      WDM coupler

Port form：X coupler（2 x 2 coupler）

          Y coupler（1 x 2 coupler）

          Star coupler（M x N coupler, M、N＞2）

          Tree coupler（1、2 x N coupler, M、N＞2）

Working bandwidth：Single window narrowband coupler（Standard Coupler）

                  Single window broadband coupler（WFC）

                  Double window broadband coupler（WIC）

Conduction mode：Singlemode Coupler

                 Multimode Coupler

3. The optical characteristic parameters of the coupler

(1) Insertion Loss, IL

Refers to the reduction value of the output port of the coupler relative to the total input optical power.

(2) Excess Loss, EL

     Refers to the reduction of the total optical power of all output ports of the coupler relative to the total input optical power.

(3) Coupling Ratio, CR

     Refers to the ratio of the optical power of each output port of the coupler to the total output power.

(4) Directivity

     Refers to the comparison value between the output optical power of the non-injected end of the input side and the total injected optical power when the coupler is working.

(5) Return Loss

     Refers to the comparison value of the output optical power at one end of the returned injected light and the total injected optical power when the coupler is working.

(6) Uniformity

     For a uniformly splitting coupler, uniformity is defined as the maximum variation of the output optical power of each output port of the coupler within the working bandwidth.   

(7) Polarization Dependent Loss, PDL

     Refers to the maximum change in the output optical power of each output port of the device when the polarization state of the transmitted optical signal changes 360°.