Performance characteristics of a WDM channel monitor based on an all-fiber AOTF with an on-fiber photodetector

We demonstrated an all-fiber wavelength-division-multiplexing channel monitor based on a narrow-band acoustooptic tunable filter (AOTF) with a built-in on-fiber photodetector. By employing a frequency-shift keying (FSK) modulation scheme, intrinsic wavelength accuracy of 0.02 nm is obtained for single-channel detection and 0.05 nm for multiple-channel detection. The minimum resolvable channel spacing is 1.0 nm. The measured channel power accuracy is <1 dB. The demonstrated channel monitor showed a polarization-dependent wavelength shift of ~0.15 nm, which is limited by the polarization mode splitting of the AOTF itself. The influence of FSK frequency spacing and the effect of channel crosstalk are also discussed.