Spectrally balanced detection for OFDI

Balanced detection is required to suppress relative intensity noise (RIN) in optical frequency domain imaging (OFDI). Because a 50/50 fiber coupler does not provide a 50% splitting ratio over the full sweeping wavelength, balanced detection by the coupler's differential output with a balanced receiver is not perfect. We have designed a new balancing scheme that detects two outputs of 50/50 coupler separately and corrects the spectral deviation in the digital domain. A better balanced detection scheme has been designed in this work. In stead of detecting the hardware balanced signal from the 50/50 fiber coupler, we digitize the two channel fringe signal independently and perform the signal balancing in the poset process. The new software based balancing significantly improves the RIN suppression. Afterward, a systematic noise analysis has been performed on the 1050nm OFDI system. The results demonstrate a RIN suppression of 33dB by spectrally corrected balanced detection, which is 11dB more that regular balanced detection.