Full duplex optical carrier radio frequency RoF link system

Abstract

The invention discloses a quadruple frequency-based scheme for realizing a base station passive full duplex millimeter wave RoF link, which is mainly used for remote transmission of a wireless signal between a base station and a central station in a Gb / s broadband millimeter wave communication system. The scheme is as shown in an attached drawing. A local oscillator with a frequency of fD / 4 drives a lithium niobate Mach-Zehnder modulator to produce a light carrier with a frequency interval of fD / 2 and two second-order sidebands. One sideband is separated by an FBG to realize single wave carrier modulation of a downlink data signal. The light carrier is transmitted to the base station through an optical fiber, and the light carrier and a double-frequency light millimeter wave signal with afrequency of fD are separated by the Mach-Zehnder modulator with a delay time difference of 1 / fD. The former is reserved as an uplink light source, and the latter produces a millimeter wave signal with the frequency of fD through photoelectric conversion, and the signal is transmitted to a user through an antenna. The uplink millimeter wave signal is processed by envelope detection to acquire a baseband signal, loaded onto a reserved light wave by a low-speed optical modulator and sent back to the central station by the optical fiber. The scheme has a plurality of advantages, so that the scheme has good application prospect.

Description

technical field [0001] The invention relates to the fields of optical communication and microwave communication, in particular to the realization of full-duplex link communication for long-distance transmission of high-frequency microwave (millimeter wave) signals using optical communication technology. Background technique [0002] Compared with wired communication, the flexibility and mobility of wireless communication make it have unparalleled advantages. In recent years, with the rapid development and wide application of wireless communication services, the bandwidth required for wireless access has increased rapidly, and low-frequency wireless spectrum resources have become increasingly scarce, which drives us to use bandwidth resources when developing new broadband wireless services Rich high frequency band. The millimeter wave in the 40-60GHz frequency band can provide bandwidth resources of several GHz, and can be used for multiple wireless communication services wi...

AI Technical Summary

Problems solved by technology

However, the frequency of the external modulator and local oscillator signal source required by the system based on the linear external modulation method to generate optical millimeter signals should not be lower than the frequency of the generated millimeter wave signal, and the required optical external modulator and local oscillator The frequency of the signal increases with the frequency of the generated millimeter-wave signal, and the high-frequency external modulator and local oscillator signal source are relatively expensive

The nonlinear external modulation technology can reduce the requirements of these two indicators. The optical carrier suppression (OCS, optical carrier suppression) modulation technology reported in the literature can halve these two indicators. The item index is reduced to 1 / 4 of the original, but the structure of this modulator is complex and the cost is high

[0005] In terms of the realization of full-duplex ROF links, many duplex link implementation schemes including light sources in the base station have been reported in the literature. The disadvantages are: the light source in the base station makes the cost high, and has high requirements for the working environment

At present, there have been reports on the implementation of full-duplex RoF links without light sources in base stations, but the generation of downlink millimeter-wave signals is generally based on linear modulation, and the frequency of the required local oscillator signal is relatively high.

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