The gain flattening filter (GFF), or gain equalizer (GEQ), is used to compensate for the uneven gain amplification at different DWDM channel by Er-doped fiber amplifier (EDFA). Broptics develops two fiber grating technologies to achieve best price/performance value for customers.
Chirped Fiber Bragg Gratings (CFBG)Chirped gratings is a sequence of grating periodic change along the transmission axis. By modifying the intensity of grating depth, a matched gain compensation profile can be created. CFBG is able to match the desired profile with minimum errors. Also, Broptics patent-pending athermal package can be applied to resist temperature drift. CFBG is the right choice for high performance EDFA design.
Long Period Gratings (LPG)Long period gratings differentiate from normal FBG by much wider grating period. The matched wavelength is coupled to cladding mode and absorbed or attenuated. By designing a series of different long gratings, a matched gain compensation profile can be created. Due to its wider period, LPG can be easier made to cover wider bandwidth. By properly select specialty fiber, LPG can be used when cost is the major concern.
| Type | LPG |
Chirped FBG |
| Wavelength range Error function Thermal stability Max attenuation Return loss |
Wide bandwidth +/- 0.5dB < 10pm/℃ <15dB Low |
S & C +/- 0.25dB < 1pm/℃ <10dB High |