Abstract

Optical communications networks rely on optical receivers to demodulate optical signals and convert the demodulated optical signal into an electrical signal. Optical receivers may be associated with one or more characteristics which can be made to vary during a transmission of an optical signal in order to improve the quality of the received signal. The present invention may determine a value for the characteristics based on an amount of optical filtering on a communications link which transmits the signal. The value for the characteristics of the receiver may be determined by observing a characteristic of a detector associated with the receiver, such as a ratio of the average photocurrents of the constructive and destructive ports of the detector. The observed characteristic of the detector may be mapped to a predetermined value for the characteristic of the receiver in a lookup table, which may be queried during operation of the receiver.

IPC Classes  ?

• H04B 10/00 - Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication

Abstract

The present application describes methods and systems that improve the optical signal to noise ratio performance of an optical network without the need to vary the free spectral range associated with a differential interferometer. This is achieved by varying an electrical bandwidth of an electronic device associated with the receiver. For example, the electrical bandwidth may vary in inverse proportion to the combined effective optical bandwidth of the transmission line carrying the optical signal. The techniques described herein a applicable to a wide variety of modulation formats, including mPSK, DPSK, DmPSK, PDmPSK, mQAM, ODB, and other direct-detection formats. Using the techniques described herein, the optical signal to noise ratio and bit error ratio performance of the optical network is improved without the need to provide costly and complex differential interferometers whose free spectral range is variable.

IPC Classes  ?

• H04B 10/69 - Electrical arrangements in the receiver

Abstract

An optical receiver includes a demodulator having a delay interferometer comprising an optical input that receives a phase modulated optical signal from a bandwidth limited transmission system. The delay interferometer has a free spectral range that is larger than a symbol rate of the phase modulated optical signal by an amount that improves receiver performance. The receiver also includes a differential detector having a first and a second photodetector. The first photodetector is optically coupled to the constructive optical output of the delay interferometer. The second photodetector is optically coupled to the destructive optical output of the delay interferometer. The differential detector combines a first electrical detection signal generated by the first photodetector and a second electrical detection signal generated by the second photodetector to generate an electrical reception signal.

IPC Classes  ?

• H04B 10/158 - Receivers