Optical balance detection method and system capable of eliminating inter-signal beat frequency interference of pdm SSB-OOFDM signals

Abstract

The invention provides an optical balance detection method and system capable of eliminating beat frequency interference between signals of PDM SSB-OOFDM signals, wherein two SSB-OOFDM signals in thePDM SSB-OOFDM signals are orthogonal in polarization, the frequency spectrums of the two paths of OOFDM signals are overlapped, and the optical carriers in the X and Y polarization directions are located on the two sides of the OOFDM signals; the receiving end quarters the optical signal by using a power divider; and then optical carriers in different polarization directions are filtered by four optical band-pass filters, the filtered optical carriers are injected into two optical balance detectors for photoelectric conversion, differential output currents of the two optical balance detectorsonly contain transmitted OFDM radio frequency signal components and direct current components, and SSBI is eliminated. By adopting the method and the system provided by the invention, SSBI-free receiving can be realized, the bandwidth does not need to be protected theoretically, and the spectrum utilization efficiency of the PDM SSB-OOFDM system is further improved. Meanwhile, a polarization beamsplitter is not used for polarization demultiplexing, so that the polarization mode dispersion problem and complex MIMO processing are avoided.

Description

technical field [0001] The invention relates to the field of optical communication, in particular to the problem of eliminating signal-to-signal beat frequency interference (SSBI) in the detection process of PDM SSB-OOFDM signals with smaller wavelength guard intervals and the problem of improving spectral efficiency in the PDM SSB-OOFDM system. Background technique [0002] At present, the Optical Orthogonal Frequency Division Multiplexing O-OFDM technology based on high-order QAM modulation has attracted widespread attention because of its high spectrum efficiency and high tolerance to fiber dispersion. Although the coherent optical OFDM (CO-OFDM) system can achieve 14bit / s / Hz spectral efficiency (Spectral Efficiency SE), the CO-OFDM system is sensitive to frequency offset and phase noise, and requires the laser linewidth of the transmitting end and receiving end Extremely narrow, which makes the design of the CO-OFDM sending and receiving system very complicated. [0003...

AI Technical Summary

Problems solved by technology

In order to ensure the elimination of the influence of SSBI, the bandwidth of GB must not be less than the bandwidth of the optical OFDM signal, which makes the spectral efficiency of the DD-OFDM system drop by more than half of that of the CO-OFDM system

Reducing GB in SSB-OOFDM can improve the SE of the system, but with the reduction of GB, the impact of SSBI on system performance will be intensified

Although some solutions to reduce the impact of SSBI on system performance have also been proposed, there are still deficiencies in system complexity and power cost

The spectral efficiency of the polarization multiplexing technology SSB-OOFDM system is improved, but the influence of SSBI still exists. At the same time, the polarization mode dispersion of the fiber link will cause the polarization directions of the two SSB-OOFDM signals that are polarization multiplexed together to randomly rotate, and then Difficulties in polarization demultiplexing of two SSB-OOFDM signals at the receiving end

Many methods to reduce the influence of SSBI on system performance have been reported in the literature, but none of them can solve the influence of polarization mode dispersion. Even if these methods eliminate SSBI, but because of the coupling between polarization modes

The traditional method to solve the polarization direction rotation caused by polarization mode dispersion is to use a polarization stabilizer (polarization stabilizer), by extracting the polarization rotation information, and then correcting the polarization direction rotation, but the cost of the polarizer is quite high, and the receiving end becomes more complex. complex

In addition, the mechanical processing of the output signal through the multi-input multi-output (Multi Input Multi Output) technology at the receiving end can also separate the two mixed signals, but it requires a rather complicated digital signal processing process, which limits the realization of the system. difficulty

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