EDFA 实用技术.ppt

Review on EDFA Kevin Lu Overview Operation principle EDFA advantage Electronic Repeater (OEO) High cost Low speed EDFA All optical and fiber compatible Wide bandwidth, 20~70 nm High gain, 20~40 dB High output power, 200mW Bit rate, modulation format, power and wavelength insensitive Low distortion and low noise (NF5dB) Gain Spectrum Gain Spectrum EDF length/US patent 6330384 Spectrum EDF length Spectrum Pumping Source 980 nm low ASE, low noise amplifier 1480 nm higher power pump laser high output power not as efficient more thermal and electrical requirement 980nm VS 1480nm Pump Source Pumping stage 1st stage high gain, low noise 2nd stage high output power 2 pumps to be more robust if one fails noise performance of amplifier is determined by the 1st stage Challenges Gain Bandwidth Widening Gain Transient Gain Flattening All band Fiber optical Amplifier GS-EDFA EDTFA RFA Gain Transient power may become too high (nonlinearity) or too low (degrade SNR) when add/drop channels transient happens in us to ms transient penalty depends on data rate, number of EDFAs and number of channels. power increase degrades performance due to SPM Power and SNR fluctuation Gain control Method Optical Attenuation Compensation Every EDFA needs compensation Same idea applies for pump power compensation Control channel method By adding/dropping the corresponding control channel when a channel is drop/add, power and SNR transient can be suppressed. Optical attenuation compensation Control channel method Gain flattening Scheme Passive equalization Pre-equalize the input signal Add dopant: fluoride based EDFA Broadband filter Hybrid pump Active equalization Acousto-Optic Tunable Filter (AOTF) Flatness of Fluoride EDFA Flatness of Fluoride EDFA Passive Gain Equalization Long-Period Fiber Grating Filter Different length of fiber has different gain spectrum. Need separate design. Wider the flatness, the higher the loss for some wavelength. 3times higher for 40nm wide gain spectrum compa