Ultra-long single span optical transmission method based on polarization multiplexing push-pull modulation encoding

Abstract

The invention relates to an ultra-long single span optical transmission method based on polarization multiplexing push-pull modulation encoding. The optical transmission method comprises the following steps: dividing a light source of a transmitting end into two paths of polarized orthogonal light by a polarization beam divider, inputting the two paths of polarized light into two identical Mach-Zehnder modulators, carrying out non-return-to-zero code modulation by data and radix-minus-one complement thereof, and transmitting to an optical fiber; and receiving optical signals on the optical fiber by a receiving end, carrying out polarization state stabilization, then separating the two polarization multiplexing optical signals, respectively receiving by a photoelectric detector and converting into two paths of electric signals which pass through a balanced receiver to obtain signal-to-noise ratio gain. The transmission method inhibits the non-linear effect at the transmitting end and improves the transmitting power, and improves the receiving signal-to-noise ratio of the system at the receiving end, thereby improving the overall system performance.

Description

technical field [0001] The invention relates to an ultra-long single-span optical transmission system, in particular to a new method for modulation, encoding and receiving of an ultra-long single-span optical transmission system based on polarization multiplexing push-pull modulation and encoding. Background technique [0002] In some special occasions, such as coastal areas, islands, deserts, forests and other places to build networks, since there is no power system available, end-to-end direct paths must be established between sites without any relay equipment, so during transmission The signal will be greatly attenuated, and the receiving end needs to perform high-gain amplification to enable the photodetector to detect the signal, which will introduce a lot of noise, degrade the signal-to-noise ratio of the signal, and thus reduce system performance. In order to improve the signal-to-noise ratio, it can be compensated by increasing the power of the transmitting end. When...

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Problems solved by technology

[0002] In some special occasions, such as coastal areas, islands, deserts, forests and other places to build networks, since there is no power system available, end-to-end direct paths must be established between sites without any relay equipment, so during transmission The signal will be greatly attenuated, and the receiving end needs to be amplified with high gain to enable the photodetector to detect the signal, which will introduce a lot of noise, degrade the signal-to-noise ratio of the signal, and thus reduce the system performance

In order to improve the signal-to-noise ratio, it can be compensated by increasing the power of the transmitting end. When using differential phase shift keying (DPSK) to modulate light intensity, since the existing system mostly uses Mach-Zehnder (MZ) modulator for modulation, when using this When modulated in the MZ mode, the MZ modulator must switch the phase through the amplitude zero point, so although the envelope of the signal in this modulation mode is constant (this point does reduce the nonlinear influence compared with the OOK modulation mode, the ordinary OOK modulation Because there is no way to decompose the light into two paths with opposite phases, the balanced receiver cannot be used), but its power is not constant, and there will be power changes when the phase is switched, which inevitably introduces nonlinear Influenced by the nonlinear effect, the transmission power cannot be increased infinitely, and the system performance is limited

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