Light transmission system and method

Abstract

A system and method for bidirectional optical transmission in one optical fiber with large transmission capacity, enabling the enlargement of transmission distance. Downward optical signals sent from one or more downward optical signal transmitters are received by one or more downward optical signal receivers via an optical fiber transmission line and upward / downward signal separating multiplexer-demultiplexers. On the other hand, upward optical signals sent from one or more upward optical signal transmitters are received by one or more upward optical signal receivers by following the opposite route. Output signals from the downward optical signal transmitter leak in the upward optical signal receiver via the upward / downward signal separating multiplexer-demultiplexer. However, there is a large difference between the frequency of the upward optical signals and that of the downward optical signals, and beat / noise components produced by interference in the two wavelengths are present outside the band of the upward optical signal receiver, thus avoiding the influence of coherent crosstalk. Additionally, power crosstalk also does not become a problem because of large isolation.

Description

technical field [0001] The present invention relates to systems and methods suitable for optical transmission in optical communication systems and the like constituting large-scale high-speed networks, and particularly to systems and methods for duplex or bidirectional in one optical fiber. Background technique [0002] Two types of optical fibers have been used in communication systems, one for uplink signals and the other for downlink signals, through high-speed optical signals with a transmission rate of more than 1Gbps (gigabits per second), or through wavelength division multiplexing (WDM) ) Optical signals obtained from high-speed optical signals in order to avoid mutual interference between uplink and downlink optical signals. [0003] On the other hand, there is a single fiber bi-directional (duplex) optical transmission technology for transmitting upstream and downstream optical signals in one optical fiber. Using this technique, the required fiber can be halved. ...

AI Technical Summary

Problems solved by technology

Therefore, the transmission capacity cannot be increased by multiplexing multiple wavelengths in the frequency band

In addition, another problem is that the loss of 0.5dB / km in 1310nm and the allowable loss in the fiber limit the transmission distance, that is, the transmission distance cannot be increased by erbium-doped fiber amplifier (EDFA)

[0007] Moreover, when the parts or components used to separate uplink and downlink are provided with poor insulation, compared with Fabry-Perot laser diodes, distributed feedback (DFB) for high-speed transmission covering many kilometers at speeds higher than 1Gbps ) lasers or integrated electroabsorption (EA) modulator light sources tend to be prone to errors due to backlight effects

Also, errors occur in signal regeneration due to light leakage from the optical transmitter to the optical receiver in the same device

Also, when the transmitter optical power is increased for longer distance transmission, stimulated Brillouin scattering occurs in the opposite direction of the optical signal, which affects the optical transmitter and optical receiver, causing errors

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