We propose and demonstrate a method of detecting the optical carrier frequency of an optical data stream using a disk-shaped wavelength-tunable optical bandpass filter operated in the synchroscan mode. The method is based on a differential technique that uses an S-shaped curve obtained from divided data streams. A bidirectional configuration with a delay line enables the data streams not only to pass through the filter at a different time but also to enter each photodiode at the same time. Consequently, pattern-oriented noise, which degrades the accuracy, can be eliminated by an optimized low-pass filter. An experimental demonstration carried out for optical signals with a non-return-to-zero format 2^7 - 1 pattern at 150 Mbit/s verifies the method. A high resolution of 100 MHz is achieved with a filter having a transmission bandwidth of 0.06 nm. This performance is promising for photonic networks that manage a large number of optical channels multiplexed in the frequency domain.
© 2004 Optical Society of AmericaPDF Article