Return-to-zero code super long distance transmission method and equipment

Abstract

The invention discloses a nulling code super long distance transmission method and apparatus characterized by that, clock signal synchronous to the data signal is directly used to modulate the laser device to produce RZ optical pulse signal, and make the output RZ optical pulse signal possess the time-varying frequency i.e. chirp, whose symbol contrary to the chirp symbol resulted in by the RZ optical pulse signal because of the self phase modulation (SPM) in the process of the optical fiber transmission, thus saving the RZ pulse generation modulator and the corresponding single-purpose driver, and realizing a longer transmission range.

Description

Technical field: [0001] The invention relates to a return-to-zero code (NZ) optical signal ultra-long-distance transmission method and device. Background technique: [0002] The signal transmission patterns used in optical transmission systems are usually NRZ (non-return-to-zero code) and RZ. The width of the "1" pulse of the NRZ code is equal to the 1 bit period of the transmission signal, and the width of the "1" pulse of the RZ code Less than half of the 1-bit period of the transmitted signal. Because the transmission technology cost of NRZ coding is low, most commercial optical transmission systems are SDH / SONET (Optical Synchronous Digital Transmission Network) or DWDM (Dense Wavelength Division Multiplexing) systems using NRZ codes. [0003] However, the transmission distance of the NRZ code optical transmission system is limited. Usually after transmission of 500-600km, it is difficult to receive correctly due to the deterioration of the OSNR (Optical Signal-to-Noise...

AI Technical Summary

Problems solved by technology

In order to achieve ultra-long-distance transmission, figure 1 The amplifier in can be the combination of RAMAN amplifier or RAMAN amplifier and EDFA amplifier, and this technology has following disadvantages: 1, cost is high, because RAMAN amplifier utilizes the non-linear effect in the optical fiber, conversion efficiency is low, to realize the amplification of optical signal, The pump power is relatively large, generally reaching more than 1W, and the high-power pump brings about an increase in cost

2. Poor security, as mentioned in 1, high-power pumps cause potential safety hazards

3. It is difficult to maintain the system. Also due to the high pump power, higher requirements are put forward for system maintenance. For example, if the end face of the optical fiber is not clean, the end face will be damaged, etc.

This implementation scheme has the following disadvantages: 1. In the case of the same average power as the NRZ code, the power of the RZ pulse is relatively high, which easily causes nonlinear effects, distorts the waveform, and affects the signal quality.

2. The implementation cost is high

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