Transmitter for generating various 16QAM (Quadrature Amplitude Modulation) code types

Abstract

The invention relates to an optical transmitter for generating various 16QAM (Quadrature Amplitude Modulation) code types. A data source generates two paths of signals for carrying out power division to obtain four paths of data; then two paths of signals drive a double-parallel modulator to obtain four constellation points; four levels obtained by laminating another two signals are used for driving a phase modulator; and finally, different QAM code types can be obtained by simple adjusting. The transmitter for generating various 16QAM code types can generate three different 16QAM code types by adopting a transmitter structure based on a double-drive modulation DPMZM and a cascade phase modulator, namely a square 16QAM code type, a star-shaped 16QAM code type and a 16APSK (Amplitude PhaseShift Keying) modulation code type, has high flexibility and can be used for different transmission systems.

Description

technical field [0001] The invention relates to an optical transmitter in the technical field of optical communication, in particular to a transmitter generating various 16QAM code patterns. In particular, it refers to an optical transmitter that generates a variety of 16QAM patterns, which is suitable for high-speed optical fiber communication systems and networks. Background technique [0002] With the popularization of high-speed Ethernet and the development of multimedia services, people put forward higher requirements on the communication capacity that the existing optical fiber communication system based on wavelength division multiplexing (WDM) technology can support. To increase the capacity of the existing WDM communication system, there are two main solutions: [0003] One is to expand the available wavelength range of the WDM system, such as using the L-band. This requires the design of corresponding L-band equipment and devices, because the equipment and device...

AI Technical Summary

Problems solved by technology

Although this scheme can obtain the square-16QAM modulation pattern with only one integrated modulator, there are also problems in this scheme: from the existing conditions, it is still very difficult to integrate high-speed devices, because the electrical speed After more than 50G, the performance will become poor and very expensive

[0009] Second, in the patent "16QAM modulation pattern optical transmitter based on a single dual-driver MZM" (patent No. 200810126898.1), a star-16QAM modulation pattern generation scheme is proposed, which uses a dual-driver modulator Generated (composed of two parallel phase modulators PM), each phase modulator is driven by a four-level signal to obtain a QPSK signal respectively, and then adjust the phase difference of the two signals so that the phase difference is 45°, and then pass The star-16QAM modulation pattern can be obtained by vector superposition. This scheme has the following disadvantages: 1. Two four-level signals need to be used, which increases the intersymbol interference (ISI) problem of the optical signal and reduces the system performance.

2. It is difficult to generate a good quality four-level signal with two high-speed two-level signals

3. The noise on the electrical signal is directly mapped to the phase of the optical signal, affecting the signal-to-noise ratio

This solution has the following problems: 1. It needs to use 3 modulators, the system structure is complex and the cost is high; 2. It needs precise synchronization between the driving signals of the 3 modulators, and the adjustment is more complicated; 3. It uses 3 modulators Cumulative insertion loss is large

Images