Control method of IQ modulator and system thereof

Abstract

The invention discloses a control method of an IQ modulator and a system thereof. The control method comprises the following steps of adding disturbance signals of a first disturbance frequency f1 and a second disturbance frequency f2 in an I bias voltage and a Q bias voltage of a light IQ modulator; detecting an output light signal output of the light IQ modulator and the added disturbance signals in real time, and monitoring direct current light power and calculating a correlation coefficient of the input disturbance signals and the output light signal; and using a light power value and the correlation coefficient to carry out feedback adjusting on the bias voltages of the light IQ modulator so that a bias state of the light IQ modulator satisfies an adjusting object. In the invention, through establishing connection between a bias voltage VI of an I path, a bias voltage VQ of Q path control and a bias voltage VP of a P path and the first disturbance frequency f1 and the second disturbance frequency f2, spectrum analysis in the prior art is replaced so that a calculating method is simplified; and an adjusting process possesses directivity, and a bias resolution of a control signal is less than 0.005Vpi.

Description

technical field [0001] The present invention relates to the communication field, in particular to a method and system for controlling an IQ modulator. Background technique [0002] Optical IQ modulation refers to optical in-phase / quadrature modulation (In-phase and Quadraturephase, IQ). Since this modulation technology can be used to generate various optical-carrying radio frequency signals in complex modulation formats related to amplitude and phase, optical IQ modulation technology is widely used in the field of optical communication. Such as figure 1 As shown, the IQ modulator is composed of two MZM modulators (Mach-Zehnder modulators) and a phase delay P, and the I-way MZM modulator (MZM I) and the Q-way MZM modulator (MZM Q) are respectively for the optical The two orthogonal phases of the carrier signal are modulated, and the phase delay P ensures the orthogonality of the two optical carrier phases. Due to the sensitivity of the IQ modulator to temperature and stres...

AI Technical Summary

Problems solved by technology

[0005] In the non-patent literature (Gui T, Li C, Yang Q, et al. Auto bias control technique foroptical OFDM transmitter with bias dithering. [J]. Optics Express, 2013, 21 (5): 5833-5841.) published a The automatic control method of a kind of IQ modulator, this method needs to do frequency spectrum analysis (FFT calculation) in microcontroller (MCU), so calculation process is comparatively complicated; And in this method, the power of IQ modulator and relative linear point The square of the control voltage is positively correlated. When adjusting the bias voltage, the power change of the IQ modulator is non-monotonic. It needs to scan and detect in a relatively large voltage range, which affects its adjustment speed and sensitivity.

If the IQ modulator uses the above method to correct the bias point during use, it will cause fluctuations in transmission, which will affect its control efficiency and accuracy

Images