Patent ID: 9438352
Filing Date: 2016-09-06
CPC Classification: H04B

Claim Text:
1. A quadrature phase shift keying (QPSK) signal conjugate relationship identification method, wherein the method comprises: controlling a QPSK modulator to receive a first binary sequence signal, using the first binary sequence signal to modulate an optical signal to obtain a first signal, and determining, within a first predetermined range, a first bias voltage in the QPSK modulator, so that the first signal at the first bias voltage is a QPSK signal and a root mean square power of the first signal at the first bias voltage is the smallest; controlling the QPSK modulator to receive a second binary sequence signal, using the second binary sequence signal to modulate the optical signal to obtain a second signal, determining a second range within the first predetermined range according to the first bias voltage, and determining, within the second range, a second bias voltage in the QPSK modulator, so that a root mean square power of the second signal at the second bias voltage is the smallest; and determining a conjugate relationship of the QPSK signal according to a value relationship between the first bias voltage and the second bias voltage; wherein determining the first bias voltage in the QPSK modulator comprises: controlling a child Mach-Zehnder (MZ) modulator of the QPSK modulator to work at a null point; injecting a first disturbance signal into a bias control end of a parent MZ modulator of the QPSK modulator; performing optical-to-electrical conversion and filtering on the first signal to obtain a first electrical signal; performing root mean square power detection on the first electrical signal to obtain a first feedback signal; using a first reference signal to perform synchronous detection on the first feedback signal to obtain a first error signal, wherein the first reference signal is a signal that is the same as the first disturbance signal; and adjusting a bias voltage of the parent MZ modulator according to the first error signal, and when the first error signal is null, determining that the bias voltage of the parent MZ modulator is the first bias voltage; and determining the second bias voltage in the QPSK modulator comprises: controlling the child MZ modulator to work at a null point; injecting a second disturbance signal into the bias control end of the parent MZ modulator; performing optical-to-electrical conversion and filtering on the second signal to obtain a second electrical signal; performing root mean square power detection on the second electrical signal to obtain a second feedback signal; using a second reference signal to perform synchronous detection on the second feedback signal to obtain a second error signal, wherein the second reference signal is a signal that is the same as the second disturbance signal; and adjusting the bias voltage of the parent MZ modulator according to the second error signal, and when the second error signal is null, determining that the bias voltage of the parent MZ modulator is the second bias voltage.