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Two polarization-independent Michelson fiber interferometers with different optical delays were used to measure the in-band OSNR of an optical signal from 5 to 30dB within an accuracy of 0.5dB. Using an expansion of the amplitude autocorrelation function of the signal around zero delay, it was possible to perform measurements without any prior knowledge of the signal. The system is shown to be immune to the effects of modulation frequency (up to 10G), partially and fully polarized noise, chromatic dispersion and poorly biased modulators.

Abstract:In this paper, the polarization response of a GaAs based twophoton absorption microcavity photodetector has been studied. The deviation in the dependence of the detector response from that of bulk GaAs is shown to be due to the birefringence of the cavity. A theoretical model based on the convolution of the cavity birefringence and the polarization dependence of two-photon absorption in GaAs is described and shown to match the measured polarization dependence of the microcavity detector very well.

An in-band optical signal-to-noise ratio (OSNR) monitoring technique based on a Michelson fiber interferometer and a linear polarizer is presented in this letter. OSNR values of up to 25 ± 0.5 dB were measured for 10-G nonreturn-tozero-differential phase-OOK (NRZ-OOK) and NRZ-differential phase-shift keyed (NRZ-DPSK) signals without prior knowledge of the signal coherence properties. Measurements were also carried out with signals having 680 ps/nm of chromatic dispersion.

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