to the sum of the sagnac phase shift and the phase shift produced by the modulator 16 a summing junction 40 receives a signal input from the phase modulator 16 and a signal ssf u03c9 that represents the phase shift induced by the angular rate u03c9 where ssf is the sagnac scale factor of the fiber gyro 12 the summing junction 40 adds the signal received from the phase modulator 16 by the scale factor to produce a signal that is input to the fiber gyro 12 the fiber gyro 12 uses the sagnac effect to produce a signal i 0 2 ue89e sin ue89e ue89e u03c6 m where u03c6 m is the phase difference between the modulated counter propagating waves in the sensing coil the optical signal output of the fiber gyro 12 is converted to an electrical signal by the photodetector 18 the photodetector 18 has a scale factor k pd which relates the electrical current output from the photodetector 18 to the optical power incident thereon the photodetector typically has a scale factor k pd 0 9 a w the photodetector output is then amplified by a transimpedance amplifier 42 that has a scale factor k ti the transimpedance amplifier 42 is connected between the photodetector 18 and the variable gain amplifier 20 and serves to match the output impedance of the photodetector 18 to the input impedance of the variable gain amplifier 20 the amplified.