Phase monitoring device, phase control device of optical DQPSK receiver and its method

Abstract

I branch is provided with a first interferometer, a first balanced optical detector, and a first data recovery circuit. Q branch is provided with a second interferometer, a second balanced optical detector and a second data recovery circuit. In I branch, a mixer multiples input signal of the first data recovery circuit with output signal of the second recovery circuit. An averaging circuit averages output signal of the mixer. In Q branch, a mixer multiples input signal of the second data recovery circuit with output signal of the first recovery circuit. An averaging circuit averages output signal of the mixer. A first phase control apparatus controls the phase of a phase shifter comprised in the first interferometer based on the output signal of the averaging circuit. A second phase control apparatus, in the same manner, controls the phase of a phase shifter comprised in the second interferometer.

Description

technical field [0001] The present invention relates to optical differential quadrature phase shift keying (optical DQPSK) receivers, and more particularly, to phase monitoring devices, active phase control devices and methods for optical DQPSK receivers. Background technique [0002] Although the capabilities of optical communication systems have grown rapidly during the past decade, the modulation technique used in most implementations remains binary amplitude shift keying in either the non-return-to-zero (NRZ) format or the return-to-zero (RZ) format (Also known as On-Off Keying (OOK)). More recently, alternative modulation and demodulation techniques have been employed in optical communications, such as duobinary, carrier-suppress-return-to-zero (CSRZ), differential phase-shift keying (DPSK). In the DPSK format, information is carried by the phase change between two adjacent symbols. Phase variation is limited to 0 and π in binary DPSK. If the phase change can be 0, π...

AI Technical Summary

Problems solved by technology

[0006] 1. Phase misalignment will cause excessive OSNR deterioration

[0007] 2. Peak detection only judges whether the actual phase is the target value

It cannot judge whether the actual phase is greater than or less than the target value

[0008] 3. The peak detection signal is usually a quadratic function of the phase error, so the sensitivity of the peak detection signal relative to the actual phase error decreases as the phase error approaches zero

As a result, the phase control accuracy is not high

[0009] 4. The phase control speed is limited by the jitter frequency

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