Polarization diversity detection performance of 2.4 Gbit/s CPFSK heterodyne system

Abstract

AbstractIn the practical implementation of the coherent optical transmission system, it is important to establish the techniques for stabilizing the optical frequency considering the actual environmental condition, as well as a technique for compensating for the variation of the state of polarization in the usual single‐mode optical fiber cable.This paper considers the application of the polarization diversity receiver to the CPFSK heterodyne delay detection in the 2.4‐Gbil/s band and discusses the construction and performance. The regenerative repeater equipment is designed in a compact form to be implemented in a commercial rack (INS cabinet rack). Using the designed equipment and the existing trunk fiber transmission route, an experiment in the actual site is conducted and the results are shown.The first part of this paper presents the construction of both the automatic frequency control (AFC) system and the automatic gain control (AGC) system suited to the polarization diversity system. The design guides are presented for the required frequency response speeds of AFC and AGC, the required frequency stability of AFC, and the response performance to the fluctuation of polarization. A high‐output, high‐sensitivity 2.4‐Gbit/s regenerative repeater equipment (with repeater gain above 48 dB) is realized with the overall performance that the variation of optical received sensitivity against the polarization fluctuation can be suppressed to within 0.5 dB.Finally, the stable operation of the equipment is verified by the experiment at the actual site, and the practical usefulness is indicates.