OFDM radio-on-fiber communication system for generating optical millimeter wave by suppressing modulation of optical carrier

Abstract

The invention discloses an OFDM radio-on-fiber communication system, which combines the radio-on-fiber communication technology with wireless OFDM technology, utilizes anti-multipath time-delay characteristic of OFDM signals and the characteristic of lower transmission speed of subcarrier and the like to resist the influence of dispersion on signals in optical fiber transmission and increases transmission distance. The OFDM signal and the radio-frequency sine wave signal are mixed to drive an intensity modulator so as to lead the continuous optical wave of the intensity modulator generated to a distributed feedback laser to realize suppressing modulation of the carrier; the optical carrier loaded with the OFDM signal is transmitted to a base station by the optical carrier; at the base station, firstly, a photoelectric detector converts the optical millimeter wave signal into the electric millimeter wave signal and finally the modulation of the OFDM signal is realized. The OFDM-over-fiber communication system also can be realized by using a dual-intensity modulator; the main working process is as follows: the distributed feedback laser generates continuous optical wave; the sine wave signal generated by a radio-frequency signal source drives the dual-intensity modulator; the suppressing modulation of the carrier is realized to the continuous optical wave; the OFDM signal generation module generates the OFDM signal; a single-arm intensity modulator loads the OFDM signal to the optical millimeter wave with suppressed carrier; and finally the OFDM signal is transmitted to the base station by the optical fiber. The millimeter wave generation method of the optical carrier OFDM signal and the radio-on-fiber communication system composed thereby can resist the influence of on signals in the optical fiber transmission, increase the transmission distance and reduce the cost of long-distance communication system.

Description

(1) Technical field [0001] The invention belongs to the technical field of communication systems for transmitting wireless Orthogonal Frequency Division Multiplexing (OFDM) signals (abbreviated as OFDM-over-Fiber) in optical fibers. (2) Background technology [0002] Optical fiber-wireless system (Radio-Over-Fiber System, referred to as ROF system) will become the most promising technology to solve broadband wireless access. The ROF system uploads the millimeter wave and data signals to the optical carrier at the same time in the central station, and transmits them to the base station. In the base station, only simple photoelectric conversion and amplification are required, so the structure of the base station can be simplified. Therefore, the ROF system meets the requirements of millimeter wave communication with characteristics such as low price, large bandwidth, high performance, and low transmission loss. [0003] The generation of optical millimeter wave is one of the ...

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Problems solved by technology

[0005] In view of the above situation, the present invention solves the problem that the millimeter wave generated by carrier suppression is affected by dispersion during optical fiber transmission, thereby limiting the transmission distance. Using the OFDM signal of the multi-carrier system, the high-speed data stream can be converted into multiple low-speed data streams , increasing the time gap per bit, thereby increasing the transmission distance

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