Method and apparatus for modulating and demodulating signal of optical fiber radio system

An optical fiber radio and signal modulation technology, applied in the field of optical communication, can solve the problems of improving the transmission performance and stability of the system, requiring very high precision of demodulation equipment, and difficulty in demodulation, so as to reduce costs, improve stability, and overcome harsh conditions. desired effect

Inactive Publication Date: 2009-08-19
TSINGHUA UNIV
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0003] Generally, phase modulation has better performance than intensity modulation, such as higher bandwidth utilization and better anti-interference performance. The proportion of phase modulation in existing optical fiber radio systems is also increasing. The baseband digital signal directly phase-modulates the optical carrier, and then transmits after up-conversion. This modulation method is very mature, and the physical and mathematical analysis are very comprehensive. However, this method encounters difficulties in demodulation. The accuracy requirements of the equipment are very high, which is not conducive to further improving the transmission performance and stability of the system

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  • Method and apparatus for modulating and demodulating signal of optical fiber radio system
  • Method and apparatus for modulating and demodulating signal of optical fiber radio system
  • Method and apparatus for modulating and demodulating signal of optical fiber radio system

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Embodiment 1

[0051] A signal modulation and demodulation method of an optical fiber radio system according to the present invention is used for signal modulation and demodulation between a central station and a wireless terminal, such as figure 1 As shown, the method includes the steps of:

[0052] In the central station, the downlink baseband digital signal is converted into an analog signal in a certain format. In this embodiment, the downlink baseband digital signal is used to modulate the original millimeter wave generator generated by the millimeter wave generator in a binary phase-shift keying BPSK (binaryphase-shift keying) modulation mode. Wave electric signal obtains described analog signal, certainly also can adopt other modulating mode to modulate analog signal with downlink baseband digital signal and carry out up-conversion;

[0053] Using the analog signal to phase-modulate the original optical carrier, and transmitting the phase-modulated optical carrier to the base station ...

Embodiment 2

[0059] The signal modulation and demodulation device of the optical fiber radio system in this embodiment is used for the signal modulation and demodulation between the central station and the wireless terminal, such as figure 2 As shown, the device includes:

[0060] A laser, set at the central station, is used to generate the original optical carrier;

[0061] The up-converter is provided with a central station, which is used to convert the downlink baseband digital signal into an analog signal at the central station. In this embodiment, it is specifically a BPSK modulator, which is used to use the downlink baseband digital signal to modulate the millimeter wave generator in BPSK modulation to generate The original millimeter-wave electrical signal of obtaining the analog signal;

[0062] A phase modulator, arranged at the central station, is used to use the analog signal to phase-modulate the original optical carrier, and transmit the phase-modulated optical carrier to th...

Embodiment 3

[0068] In this embodiment, except having the same parts as Embodiment 2, such as image 3 As shown, the device also includes: a first polarization controller, connected between the tunable laser TL (Tunable laser) and the phase modulator, for adjusting the polarization state of the original optical carrier generated by the TL; an erbium-doped fiber amplifier EDFA, used to amplify the optical carrier received by the base station before the delay; the second polarization controller, connected between the erbium-doped fiber amplifier and the delayer, used to polarize the amplified electrical signal state adjustment; the electric amplifier is used to amplify the electric signal before the wireless terminal mixes the electric signal; Low-pass filtering is realized by using an electric low-pass filter LP (Electronic low pass filter). The downlink baseband digital signal is specifically a pseudo-random sequence signal.

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Abstract

The invention relates to a signal modulation and demodulation method of an optical fiber wireless system, and a device thereof. The method comprises the following steps: a downlink baseband digital signal is modulated onto a microwave and transferred to an analogue signal by a central station; phase modulation is applied to the analogue signal to obtain an original light carrier, and the light carrier obtained by the phase modulation is transmitted to a base station; after being synthesized in a delay mode by the base station, the light carrier is converted into an electric signal which is sent to a wireless terminal; frequency mixing and low-pass filtering are carried out to the electric signal received by the wireless terminal, and the downlink baseband digital signal is obtained by demodulation. The device comprises an upper frequency converter used for converting the downlink baseband digital signal into the analogue signal at the central station, and a phase adapter used for carrying out phase modulation to the original light carrier by using the analogue signal and transmitting the light carrier obtained by the phase modulation to the base station. The method and the device not only take the advantage of the phase modulation, but also overcome harsh requirement on high accuracy of demodulation equipment and do not need Mach-Zehnder interferometer required by the traditional demodulation, thus improving the stability of the base station.

Description

technical field [0001] The invention relates to the technical field of optical communication, in particular to an optical fiber radio system. Background technique [0002] With the rapid development of wireless communication in recent years, wireless users have increased year by year, services have become more diversified, and data services have risen sharply, making the demand for broadband wireless signals and carrier frequencies to expand to high-frequency millimeter waves increasingly urgent. The electronic bottleneck of electronic devices makes it far from meeting the growth of future demand, and the millimeter-wave optical fiber radio technology uses the broadband and low-loss characteristics of optical fiber technology to provide the necessary huge bandwidth and transmission quality for the comprehensive transmission of various wireless service information , can effectively solve the difficult problems faced by the development of broadband wireless communication netwo...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H04B10/12H04B10/2575
Inventor 郑小平武熙闻和张汉一
Owner TSINGHUA UNIV
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