CN1933377A - Bidirectional transmission structure of millimeter wave optical fiber transmission system based on insertion pilot frequency method and signal transmitting method - Google Patents

Abstract

The invention relates to a bidirectional transmission structure and a signal transmission method of a millimeter wave optical fiber transmission system based on an insertion pilot method. In the present invention, the pilot is inserted into the baseband signal at the sending end of the central station, that is, the mixed signal of the baseband signal and the pilot sine wave is used to modulate the intensity of the light wave, and the phase of the light wave is modulated with a frequency-swept sine wave, and the Fabry-Perot optical filter is used. After the optical detector of the base station completes the photoelectric conversion, the millimeter-wave carrier and the millimeter-wave reference local oscillator carrying the baseband signal are extracted respectively through two millimeter-wave filters with different parameters, so as to realize the downlink function of the system At the same time, the reference local oscillator required for the uplink is obtained in the base station. For the uplink, mix the user millimeter wave uplink signal received by the base station with the reference local oscillator obtained in the downlink to obtain an uplink intermediate frequency subcarrier, and use the intermediate frequency subcarrier to directly modulate the light source in the base station, and the receiving end of the central station After the photoelectric conversion, the frequency is down-converted to take out the uplink baseband signal, so as to realize the uplink of the system.

Description

Based on the transmitted in both directions structure and the method for transmitting signals that insert the pilot tone system millimeter wave optical fibre transmission system

Technical field

The present invention relates to a kind of transmitted in both directions structure and method for transmitting signals of millimeter wave optical fibre transmission system, particularly a kind of based on the transmitted in both directions structure and the method for transmitting signals that insert the pilot tone system millimeter wave optical fibre transmission system.

Background technology

In recent years, the rapid increase of wireless communication capacity and class of business made the existing communication frequency spectrum become very crowded, and the Application and Development millimeter wave frequency band becomes inevitable developing direction.Advantages such as it is abundant that millimeter-wave communication system has bandwidth resources, is easy to channeling, and equipment is light; But because water smoke and oxygen are very serious to signal attenuation in the millimeter wave available window, so the aerial transmission range of millimeter wave is limited, just must roll up the millimeter wave base station in order to reach certain network coverage area, this will cause system cost significantly to rise, and utilizing radio frequency optical fiber transmission technique (ROF) to transmit millimeter wave is to reduce the solution that system cost improves system effectiveness.The radio frequency optical fiber transmission technique concentrates on the minority central station with every function of signal processing, and a central station connects several base stations by the bidirectional optical fiber link, and the base station is transparent to baseband signal, realizes the conversion between light wave/millimeter wave, the millimeter wave/light wave.

The key that realizes millimeter wave ROF system is to avoid the optical fiber dispersion influence, reduces the base station cost, makes its equipment lightness.The content that specifically comprises two aspects, the one, in the down link, the generation of millimeter wave carrier and transmission in the base station, the 2nd, in the up link, the generation of base station millimeter wave local oscillator.

Koonen.T. wait the people at Photonic Network Communications, Netherlands, KluwerAcademic Publisher, 5:2, among the In-HouseNetwork Using Multimode Polymer Optical Fiber for Broadband Wireless Services that delivers on pp.177～187 (" photonic network communication " 2003) (" adopting the professional internal home network of broadband wireless of multimodal polymer optical fiber "), provided the structure of down link of the 5.4GHz of a kind of optics times multiplication, its main goal in research is to adopt multimodal polymer optical fiber to produce microwave signal as the fibre system of link medium, does not relate to the generation of millimeter wave and the design problem of up link in this article.

Solution at up link mainly contains two kinds at present, the one, the direct microwave signal modulated light wave that receives with the base station, though architecture of base station is simple, but when microwave frequency is higher, must use the external modulator of two-forty, increased the base station cost, and high-frequency microwave-subcarrier signal can cause the optical fiber link dispersive influence serious; The 2nd, in the base station, use the millimeter wave local oscillator, this is a kind of to improve the scheme that base station cost and complexity exchange low chromatic dispersion transmission for.

Summary of the invention:

The object of the present invention is to provide a kind of deficiency that overcomes existing two-way link design, a kind of transmitted in both directions structure and signal method that inserts the pilot tone system millimeter wave optical fibre transmission system is provided, make system base-station simple in structure, to satisfy the practical needs of millimeter wave optical fibre transmission system.

For achieving the above object, the present invention adopts following technical proposals:

A kind of based on the transmitted in both directions structure of inserting the pilot tone system millimeter wave optical fibre transmission system, constitute uplink downlink by central station and base station by the interconnection of optical fiber bidirectional transmission link, it is characterized in that:

1), the structure of described down link is: the laser in the central station links to each other by tail optical fiber with a phase-modulator, a frequency sweep sine-wave oscillator is connected to the input of a microwave amplifier by electric lead, the output of microwave amplifier connects the control electrode of described phase-modulator by electric lead, the output of phase-modulator connects an intensity modulator by tail optical fiber, there are a pilot oscillator and downgoing baseband signal to be connected to two inputs of a wave multiplexer respectively by electric lead, the output of wave multiplexer connects the control electrode of described intensity modulator by electric lead, the output of intensity modulator connects a Fabry-Perot optical filter by tail optical fiber, the output of Fabry-Perot optical filter connects an erbium-doped fiber amplifier EDFA by tail optical fiber, and the output of erbium-doped fiber amplifier EDFA is connected to described optical fiber bidirectional transmission link by tail optical fiber; The end of described optical fiber bidirectional transmission link connects the input of a photo-detector in the base station, the output of photo-detector connects the input that a millimeter wave amplifies splitter by electric lead, millimeter wave amplifies the input of one road output of splitter by a millimeter wave band pass filter of electric lead connection, the output of millimeter wave band pass filter connects the port one of one three end circulator by electric lead, the port 2 of three end circulators connects antenna by feeder line, millimeter-wave signal is launched through antenna, thereby realizes the downlink transfer function of signal; Other one road output that millimeter wave amplifies splitter connects the input of another millimeter wave band pass filter, obtains the millimeter wave reference local oscillator at the output of this millimeter wave band pass filter, for the uplink signal transmission provides the down-conversion reference local oscillator;

2), the structure of described up link is: the subscriber signal of the antenna collection in the base station enters described three end circulator port 2 by feeder line, by 3 outputs of three end circulator port, three end circulator port 3 connect the input of a low noise amplifier by electric lead, the low noise amplifier output connects an input of a millimeter wave mixer by electric lead, the millimeter wave reference local oscillator of the output output of described millimeter wave band pass filter is added to another input of millimeter wave mixer by electric lead, the output of millimeter wave mixer connects an intermediate frequency filtering amplifier input terminal by electric lead, the output of intermediate frequency filtering amplifier is by the input of a laser of electric lead connection, and the light wave of this laser output connects the optical fiber bidirectional transmission link by tail optical fiber; In central station, the input of a photo-detector connects described optical fiber bidirectional transmission link, the output of this photo-detector is connected to an input of intermediate frequency mixer by electric lead, another input of intermediate frequency mixer connects the output of pilot oscillator by electric lead, the output of intermediate frequency mixer is directly exported the user uplink baseband signal by the input of a decision device of electric lead connection at decision device.

A kind of based on the two-way signaling transmission method that inserts the pilot tone system millimeter wave optical fibre transmission system, adopt the up-down bidirectional transmission structure of above-mentioned millimeter wave optical fibre transmission system to carry out the two-way signaling transmission, it is characterized in that:

1), downstream signal transmission method: with the frequency sweep sine wave light wave is carried out phase modulated at central station, mixed signal with downgoing baseband signal and pilot tone sine wave is carried out intensity modulated to light wave, and with the Fabry-Perot optical filter light wave of intensity and Phase Double remodulates is carried out filtering and produce pectination spectrum; In the base station, the light wave that comes from the central station transmission carries out light-to-current inversion by photo-detector, amplifying the signal of splitter after with light-to-current inversion with millimeter wave then amplifies and is divided into two-way, allow it respectively by two different millimeter wave band pass filters then, and obtain descending modulated wave of millimeter wave and millimeter wave reference local oscillator respectively, the descending modulated wave of millimeter wave is launched by antenna through amplifying the back, thereby realize the downstream signal transfer function, also provide the millimeter wave reference local oscillator simultaneously for uplink signal transmissions;

2), uplink signal transmission method: user's millimeter wave upward signal that the base station receives from antenna is after low noise amplifier amplifies, in frequency mixer with the mixing of described millimeter wave reference local oscillator, realize the down-conversion of signal, acquisition is subjected to the intermediate frequency subcarrier of uplink baseband signal modulation, with the direct modulated laser of intermediate frequency subcarrier, its output is transferred to the photo-detector of central station, output intermediate frequency subcarrier after light-to-current inversion, export the user uplink baseband signal through down-conversion, decision device again, thereby realize the uplink signal transmissions function.

Below the present invention is further illustrated:

The transmission course of down link signal and method are based on the optics frequency sweep method that inserts pilot tone, and specific implementation is:

Referring to Fig. 1, at central station 1 transmitting terminal, it is f that frequency sweep sine-wave oscillator 1-6 produces frequency _SwThe frequency sweep sine wave amplify rear drive LiNbO through microwave amplifier 1-7 ₃Phase-modulator 1-2, the light wave of noise spectra of semiconductor lasers 1-1 output carries out phase modulated; It is f that pilot oscillator 1-8 produces frequency _PltThe sinusoidal wave and downgoing baseband signal 1-10 of pilot tone in wave multiplexer 1-9 stack, the intensity of modulating the frequency sweep light wave with the mixed signal after the stack.The light wave electric field of intensity modulator 1-3 output is expressed as:

$E\left(t\right)=E_c\sqrt{m_a[g\left(t\right)+\cos {\mathrm{\ω}}_{\mathrm{plt}}t]}\exp ({\mathrm{j\ω}}_{c}t+\mathrm{j\β}\sin {\mathrm{\ω}}_{\mathrm{sw}}t)---\left(1\right)$

Wherein, E _cBe light wave electric field amplitude, ω _cBe the central angle frequency of light wave, ω _PltBe the angular frequency of pilot tone sine wave, ω _SwFor scanning sinusoidal wave angular frequency, g (t) is downgoing baseband signal 1-10, m _aBe modulation index, β is a phase-modulation index.

Intensity modulator 1-3 connects Fabry-Perot optical filter 1-4, and its impulse response is:

$h_{\mathrm{fp}}\left(t\right)=t^2[\mathrm{\&delta;}(t-\frac{{\mathrm{\&tau;}}_{\mathrm{fp}}}{2})+{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="A20061011670100141.png"\; state="\{\{state\}\}">r</figure-callout>}}^2\mathrm{\&delta;}(t-\frac{{3\mathrm{\&tau;}}_{\mathrm{fp}}}{2})+...+r^{2n}\mathrm{\&delta;}(t-\frac{(2n+1){\mathrm{\&tau;}}_{\mathrm{fp}}}{2})+...]---\left(2\right)$

Wherein r and t are respectively the electric field reflection coefficient and the transmission coefficient of optical filter, and t ²=1-r ², τ _FpBe light signal in time of delay back and forth of Fabry-Perot optical cavity internal reflection.

In order to satisfy the power requirement of system, the light wave of central station was A with a multiplication factor before injecting optical fiber link 2 _oErbium-doped fiber amplifier (EDFA) 1-5 the light wave of Fabry-Perot optical filter 1-4 output is amplified, so the light wave electric field expression formula of the last output of central station is:

$E\left(t\right)=\frac{E_c{A}_o(1-R)\sqrt{m_a[g\left(t\right)+{\cos \mathrm{\&omega;}}_{\mathrm{plt}}}t]}{1-{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="A20061011670100141.png"\; state="\{\{state\}\}">R</figure-callout>}}^2\exp (-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="A20061011670100141.png"\; state="\{\{state\}\}">j</figure-callout>}2{\mathrm{\&omega;}}_c{\mathrm{\&tau;}}_{\mathrm{fp}})}\left\{\exp \right[j{\mathrm{\&omega;}}_c(t-\frac{{\mathrm{\&tau;}}_{\mathrm{fp}}}{2})+\mathrm{j\&beta;}{\sin \mathrm{\&omega;}}_{\mathrm{sw}}(t-\frac{{\mathrm{\&tau;}}_{\mathrm{fp}}}{2})]$

$+\mathrm{Rexp}[j{\mathrm{\&omega;}}_c(t-\frac{{3\mathrm{\&tau;}}_{\mathrm{fp}}}{2})+j{\mathrm{\&beta;}\sin \mathrm{\&omega;}}_{\mathrm{sw}}(t-\frac{{3\mathrm{\&tau;}}_{\mathrm{fp}}}{2})]\}---\left(3\right)$

Wherein R is a reflection coefficient of power, R=r ²

Base station 3 receiving terminals directly carry out light-to-current inversion with photo-detector 3-1 with the light wave that receives, and the photoelectric current of output can be expressed as:

$i_d\left(t\right)=\frac{i_0{A_o}^2{(1-R)}^2{m}_a[g\left(t\right)+{\cos \mathrm{\&omega;}}_{\mathrm{plt}}t]}{1+R^4-2{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="A20061011670100141.png"\; state="\{\{state\}\}">R</figure-callout>}}^2\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="A20061011670100141.png"\; state="\{\{state\}\}">cos</figure-callout>}2{\mathrm{\&omega;}}_c{\mathrm{\&tau;}}_{\mathrm{fp}}}\{1+{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="A20061011670100141.png"\; state="\{\{state\}\}">R</figure-callout>}}^2+2R\cos [{\mathrm{\&omega;}}_c{\mathrm{\&tau;}}_{\mathrm{fp}}+2\mathrm{\&beta;}\sin \left(\frac{{\mathrm{\&omega;}}_{\mathrm{sw}}{\mathrm{\&tau;}}_{\mathrm{fp}}}{2}\right)\cos ({\mathrm{\&omega;}}_{\mathrm{sw}}t-{\mathrm{\&omega;}}_{\mathrm{sw}}{\mathrm{\&tau;}}_{\mathrm{fp}})\left]\right\}---\left(4\right)$

I wherein ₀Be the average light electric current, and i ₀=FP ₀, P ₀, F is respectively input optical power and the responsiveness of photo-detector 3-2.

Get τ _Fp=0.5/f _Sw, f _SwBe scanning frequency, following formula expanded into Bessel function:

$i_d\left(t\right)=\frac{i_0{A_o}^2{(1-R)}^2{m}_a[g\left(t\right)+{\cos \mathrm{\&omega;}}_{\mathrm{plt}}t]}{1+R^4-2{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="A20061011670100141.png"\; state="\{\{state\}\}">R</figure-callout>}}^2\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="A20061011670100141.png"\; state="\{\{state\}\}">cos</figure-callout>}2{\mathrm{\&omega;}}_c{\mathrm{\&tau;}}_{\mathrm{fp}}}\{1+{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="A20061011670100141.png"\; state="\{\{state\}\}">R</figure-callout>}}^2+2R\cos {\mathrm{\&omega;}}_c{\mathrm{\&tau;}}_{\mathrm{fp}}{J}_{0}2\mathrm{\&beta;}+$

$4R{\cos \mathrm{\&omega;}}_c{\mathrm{\&tau;}}_{\mathrm{fp}}\underset{n=1}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{(-1)}^n{J}_{2n}\left(2\mathrm{\&beta;}\right)\cos \left[2n({\mathrm{\&omega;}}_{\mathrm{sw}}t-{\mathrm{\&omega;}}_{\mathrm{sw}}{\mathrm{\&tau;}}_{\mathrm{fp}})\right]+$

$4R\sin {\mathrm{\&omega;}}_c{\mathrm{\&tau;}}_{\mathrm{fp}}\underset{n=1}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{(-1)}^n{J}_{2n+1}\left(2\mathrm{\&beta;}\right)\cos \left[(2n+1)({\mathrm{\&omega;}}_{\mathrm{sw}}t-{\mathrm{\&omega;}}_{\mathrm{sw}}{\mathrm{\&tau;}}_{\mathrm{fp}})\right]\}---\left(5\right)$

By expression formula (5) as can be seen, the signal of photo-detector output is to be 2n ω by frequency _Sw(2n+1) ω _SwThe amplitude-modulated wave of some frequency components is formed, by design alternative ω _cAnd τ _FpMake cos ω _cτ _Fp=1, thus make the maximization of even-order harmonic composition, odd harmonic composition (2n+1) ω in the while erasure signal _SwSo, signal is reduced to:

$i_d\left(t\right)=\frac{i_0{A_o}^2{(1-R)}^2{m}_a[g\left(t\right)+{\cos \mathrm{\&omega;}}_{\mathrm{plt}}t]}{1+R^4-2{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="A20061011670100141.png"\; state="\{\{state\}\}">R</figure-callout>}}^2\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="A20061011670100141.png"\; state="\{\{state\}\}">cos</figure-callout>}2{\mathrm{\&omega;}}_c{\mathrm{\&tau;}}_{\mathrm{fp}}}\{D+4R\underset{n=1}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{(-1)}^n{J}_{2n}\left(2\mathrm{\&beta;}\right)\cos [2n({\mathrm{\&omega;}}_{\mathrm{sw}}t-{\mathrm{\&omega;}}_{\mathrm{sw}}{\mathrm{\&tau;}}_{\mathrm{fp}})\left]\right\}---\left(6\right)$

Wherein D represents DC component, and D=1+R ²+ 2RJ ₀(2 β).

From expression formula (6) as can be seen, signal is made up of two amplitude-modulated waves, and one is that angular frequency is 2n ω _SwModulation signal is the amplitude-modulated wave of baseband signal g (t), and one is that angular frequency is 2n ω _SwModulation signal is pilot signal cos ω _PltThe amplitude-modulated wave of t.From the angle of frequency spectrum, comprised 2n ω in the signal spectrum _SwWith 2n ω _Sw± ω _PltFrequency content.Its medium frequency is 2n ω _SwComponent be the descending carrier that has carried baseband signal, frequency is 2n ω _Sw+ ω _PltOr 2n ω _Sw-ω _PltComponent can extract millimeter wave reference local oscillator as the up link down-conversion.So millimeter wave is amplified the back that splitter 3-2 is placed on photo-detector 3-1, in amplifying signal, input signal is divided into two-way output, one tunnel connection central angle frequency is 2n ω _SwMillimeter wave band pass filter 3-3 (1), thereby obtained carrying the millimeter wave carrier of baseband signal, and send through circulator three end circulator 3-4 and antenna 3-5, realize the downlink transfer function of signal.The modulated downstream signal expression formula of millimeter wave is as follows:

$i_t\left(t\right)=\frac{4i_0{A_o}^2{A}_{e1}R{(1-R)}^2{m}_{a}g\left(t\right)}{1+R^4-2{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="A20061011670100141.png"\; state="\{\{state\}\}">R</figure-callout>}}^2\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="A20061011670100141.png"\; state="\{\{state\}\}">cos</figure-callout>}2{\mathrm{\&omega;}}_c{\mathrm{\&tau;}}_{\mathrm{fp}}}{\&CenterDot;J}_{2n}\left(2\mathrm{\&beta;}\right)\cos \left[2n({\mathrm{\&omega;}}_{\mathrm{sw}}t-{\mathrm{\&omega;}}_{\mathrm{sw}}{\mathrm{\&tau;}}_{\mathrm{fp}})\right]\}---\left(7\right)$

A wherein _E1Amplify the gain of splitter 3-2 for millimeter wave.

Another road output that millimeter wave amplifies splitter 3-2 is 2n ω through the central angle frequency _Sw+ ω _PltPerhaps 2n ω _Sw-ω _PltMillimeter wave band pass filter 3-3 (2) filtering after, can provide millimeter wave reference local oscillator 3-7 for up link.

The acquisition of millimeter wave reference local oscillator 3-7 in the base station 3 is the uplink signal transmissions key technology, and after addressing this problem, it is simple relatively that the transmission course of uplink signal becomes:

The signal that in the base station 3 antenna 3-5 is received is behind three end circulator 3-4 and low noise amplifier 3-6, with the millimeter wave reference local oscillator 3-7 of above-mentioned generation through frequency mixer 3-8 down-conversion, the intermediate frequency subcarrier that taking-up is modulated by the uplink baseband signal, with intermediate frequency filtering amplifier 3-9 the filtering of intermediate frequency subcarrier is amplified, make its directly modulated laser 3-10; Be transferred to central station 3 receiving terminals by the up light wave of intermediate frequency sub-carrier modulation via optical fiber link 2; In central station 3,, obtain the intermediate frequency subcarrier, be down-converted to base band through intermediate frequency mixer 1-12 again, recover user uplink baseband signal 1-14 with decision device 1-13 then through photo-detector 1-6 light-to-current inversion.

The present invention compared with prior art, have following outstanding feature and remarkable advantage: (1) central station transmitting terminal inserts pilot tone in baseband signal, promptly use the mixed signal modulated light wave intensity of pilot tone sine wave and baseband signal, and with frequency sweep sine wave modulation phase of light wave, form the pectination frequency spectrum with the Fabry-Perot optical filter, thereby in the base station, pass through two millimeter wave filters that parameter is different, extract the millimeter wave carrier and the millimeter wave reference local oscillator of carrying baseband signal respectively, simplified base station equipment.(2) be used in the method for inserting pilot tone in the downlink transfer link and provide needed millimeter wave reference local oscillator, avoided using expensive millimeter wave local vibration source in the base station, can reduce the base station expense effectively for uplink signal transmissions down-conversion in the base station.(3) the millimeter wave local oscillator of generation of the modulated wave of down link and up link generates and all is based on the optics frequency sweep method in the base station, makes base station equipment passive.

Description of drawings:

Accompanying drawing: insert pilot tone system millimeter wave ROF system bidirectional transmission structure schematic diagram.

Number in the figure is represented:

Central station 1, optical fiber bidirectional transmission link 2, base station 3, laser 1-1, phase-modulator 1-2, intensity modulator 1-3, Fabry-Perot optical filter 1-4, erbium-doped fiber amplifier (EDFA) 1-5, frequency sweep sine-wave oscillator 1-6, microwave amplifier 1-7, pilot oscillator 1-8, wave multiplexer 1-9, downgoing baseband signal 1-10, photo-detector 1-11, intermediate frequency mixer 1-12, decision device 1-13, uplink baseband signal 1-14, photo-detector 3-1, millimeter wave amplifies splitter 3-2, millimeter wave band pass filter 3-3 (1), millimeter wave band pass filter 3-3 (2), three end circulator 3-4, antenna 3-5, low noise amplifier 3-6, millimeter wave reference local oscillator 3-7, millimeter wave mixer 3-8, intermediate frequency filtering amplifier 3-9, laser 3-10;

Embodiment:

A preferred embodiment of the present invention is: the transmitted in both directions structure of this insertion pilot tone system millimeter wave optical fibre transmission system and method for transmitting signals are the transmitted in both directions structure and the method for transmitting signals that are applied to the 40GHz fiber optic transmission system.Now be described below:

The transmitted in both directions structure of this millimeter wave optical fibre transmission system constitutes uplink downlink by central station 1 and base station 3 by 2 interconnection of optical fiber bidirectional transmission link referring to accompanying drawing:

1), the structure of described down link is: the laser 1-1 in the central station 1 links to each other by tail optical fiber with a phase-modulator 1-2, a frequency sweep sine-wave oscillator 1-6 is connected to the input of a microwave amplifier 1-7 by electric lead, the output of microwave amplifier 1-7 connects the control electrode of described phase-modulator 1-2 by electric lead, the output of phase-modulator 1-2 is by tail optical fiber bonding strength modulator 1-3, there are a pilot oscillator 1-8 and downgoing baseband signal 1-10 to be connected to two inputs of a wave multiplexer 1-9 respectively by electric lead, the output of wave multiplexer 1-9 connects the control electrode of described intensity modulator 1-3 by electric lead, the output of intensity modulator 1-3 connects a Fabry-Perot optical filter 1-4 by tail optical fiber, the output of Fabry-Perot optical filter 1-4 connects an erbium-doped fiber amplifier EDFA1-5 by tail optical fiber, and the output of erbium-doped fiber amplifier EDFA1-5 is connected to optical fiber bidirectional transmission link 2 by tail optical fiber; Described optical fiber bidirectional transmission link 2 ends connect the input of a photo-detector 3-1 in base station 3, the output of photo-detector 3-1 connects the input that a millimeter wave amplifies splitter 3-2 by electric lead, millimeter wave amplifies the input of the road output of splitter 3-2 by an electric lead millimeter wave band pass filter 3-3 of connection (1), the output of millimeter wave band pass filter 3-3 (1) connects the port one of one three end circulator 3-4 by electric lead, the port 2 of three end circulator 3-4 connects antenna 3-5 by feeder line, millimeter-wave signal is launched through antenna 3-5, thereby realizes the downlink transfer function of signal; Other one road output of millimeter wave amplification splitter 3-2 connects the input of another millimeter wave band pass filter 3-3 (2), output at this millimeter wave band pass filter 3-3 (2) obtains millimeter wave reference local oscillator 3-7, for the uplink signal transmission provides the down-conversion reference local oscillator;

2), the structure of described up link is: the subscriber signal that the antenna 3-5 in the base station 3 gathers enters described three end circulator 3-4 ports 2 by feeder line, by 3 outputs of three end circulator 3-4 ports, three end circulator 3-4 ports 3 connect the input of a low noise amplifier 3-6 by electric lead, low noise amplifier 3-6 output connects the input of a millimeter wave mixer 3-8 by electric lead, the millimeter wave reference local oscillator 3-7 of the output output of described millimeter wave band pass filter 3-3 (2) is added to another input of millimeter wave mixer 3-8 by electric lead, the output of millimeter wave mixer 3-8 connects the input of an intermediate frequency filtering amplifier 3-9 by electric lead, the output of intermediate frequency filtering amplifier 3-9 is by the input of a laser 3-10 of electric lead connection, and the light wave of this laser 3-10 output connects optical fiber bidirectional transmission link 2 by tail optical fiber; In central station 1, the input of a photo-detector 1-11 connects described optical fiber bidirectional transmission link 2, the output of this photo-detector 1-11 is connected to the input of intermediate frequency mixer 1-12 by electric lead, another input of intermediate frequency mixer 1-12 connects the output of pilot oscillator 1-8 by electric lead, the output of intermediate frequency mixer 1-12 is directly exported user uplink baseband signal 1-14 by the input of a decision device 1-13 of electric lead connection at decision device 1-13.

The two-way signaling transmission method of this insertion pilot tone system millimeter wave optical fibre transmission system is as follows:

1), downstream signal transmission method: light wave is carried out phase modulated at central station 1 usefulness frequency sweep sine wave, mixed signal with downgoing baseband signal and pilot tone sine wave is carried out intensity modulated to light wave, and with Fabry-Perot optical filter 1-4 the light wave of intensity and Phase Double remodulates is carried out filtering and produce pectination spectrum; In the base station 3, the light wave that comes from central station 1 transmission carries out light-to-current inversion by photo-detector 3-1, amplifying the signal of splitter 3-2 after with light-to-current inversion with millimeter wave then amplifies and is divided into two-way, allow it respectively by two different millimeter wave band pass filter 3-3 (1), (2) then, and obtain descending modulated wave of millimeter wave and millimeter wave reference local oscillator 3-7 respectively, the descending modulated wave of millimeter wave is launched by antenna 3-5 through amplifying the back, thereby realize the downstream signal transfer function, also provide millimeter wave reference local oscillator 3-7 simultaneously for uplink signal transmissions;

2), uplink signal transmission method: user's millimeter wave upward signal that base station 3 receives from antenna 3-5 is after low noise amplifier 3-6 amplifies, in frequency mixer 3-8 with described millimeter wave reference local oscillator 3-7 mixing, realize the down-conversion of signal, acquisition is subjected to the intermediate frequency subcarrier of uplink baseband signal modulation, with the direct modulated laser 3-10 of intermediate frequency subcarrier, its output is transferred to the photo-detector 1-11 of central station 1, output intermediate frequency subcarrier after light-to-current inversion, pass through down-conversion again, decision device output user uplink baseband signal 1-14, thus realize the uplink signal transmissions function.

The signal processing of present embodiment is as follows:

At the transmitting terminal of central station 1, the semiconductor laser 1-1 that is used as light source is operated in the 1550nm wavelength, live width 10MHz, power 10mW.It is f that frequency sweep sine-wave oscillator 1-6 produces frequency _SwThe frequency sweep sine wave of=5GHz drives LiNbO after microwave amplifier 1-7 amplifies 30dB ₃Phase-modulator 1-2.Pilot oscillator 1-8 produces f _PltAfter the downgoing baseband signal 1-5 that the pilot tone sine wave of=2GHz and speed are 100Mbps mixes, be added to the control electrode of intensity modulator 1-3 jointly, what intensity modulator 1-3 exported is the dual light wave of being modulated of phase place and intensity, and this light wave is at process FSR=10GHz (τ _FpForm pectination spectrum behind=0.1ns) the Fabry-Perot optical filter.In order to satisfy the requirement of signal transmitting power in the base station, descending light wave carried out luminous power with erbium-doped fiber amplifier (EDFA) 1-5 earlier and amplifies 20dB before sending to optical fiber link 2.The light wave electric field of the last output of central station can be expressed as:

$E\left(t\right)=\frac{E_c{A}_o(1-R)\sqrt{m_a[g\left(t\right)+{\cos \mathrm{\&omega;}}_{\mathrm{plt}}}t]}{1-{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="A20061011670100141.png"\; state="\{\{state\}\}">R</figure-callout>}}^2\exp (-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="A20061011670100141.png"\; state="\{\{state\}\}">j</figure-callout>}2{\mathrm{\&omega;}}_c{\mathrm{\&tau;}}_{\mathrm{fp}})}\left\{\exp \right[j{\mathrm{\&omega;}}_c(t-\frac{{\mathrm{\&tau;}}_{\mathrm{fp}}}{2})+\mathrm{j\&beta;}{\sin \mathrm{\&omega;}}_{\mathrm{sw}}(t-\frac{{\mathrm{\&tau;}}_{\mathrm{fp}}}{2})$

$+\mathrm{Rexp}[j{\mathrm{\&omega;}}_c(t-\frac{{3\mathrm{\&tau;}}_{\mathrm{fp}}}{2})+j{\mathrm{\&beta;}\sin \mathrm{\&omega;}}_{\mathrm{sw}}(t-\frac{{3\mathrm{\&tau;}}_{\mathrm{fp}}}{2})]\}---\left(3\right)$

Wherein, E _cBe light wave electric field amplitude, ω _cBe the central angle frequency of light wave, ω _PltBe the angular frequency of pilot tone sine wave, ω _SwFor scanning sinusoidal wave angular frequency, g (t) is downgoing baseband signal 1-10, m _aBe modulation index, β is a phase-modulation index, τ _FpBe light signal in time of delay back and forth of Fabry-Perot optical cavity internal reflection, R is the reflection coefficient of power of Fabry-Perot optical filter, A _oMultiplication factor for erbium-doped fiber amplifier (EDFA).

In base station 3 with descending light wave after photo-detector 3-1 light-to-current inversion, the photoelectric current of output expands into Bessel function:

$i_d\left(t\right)=\frac{i_0{A_o}^2{(1-R)}^2{m}_a[g\left(t\right)+{\cos \mathrm{\&omega;}}_{\mathrm{plt}}t]}{1+R^4-2{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="A20061011670100141.png"\; state="\{\{state\}\}">R</figure-callout>}}^2\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="A20061011670100141.png"\; state="\{\{state\}\}">cos</figure-callout>}2{\mathrm{\&omega;}}_c{\mathrm{\&tau;}}_{\mathrm{fp}}}\{1+{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="A20061011670100141.png"\; state="\{\{state\}\}">R</figure-callout>}}^2+2R\cos {\mathrm{\&omega;}}_c{\mathrm{\&tau;}}_{\mathrm{fp}}{J}_0\left(2\mathrm{\&beta;}\right)+$

$4R{\cos \mathrm{\&omega;}}_c{\mathrm{\&tau;}}_{\mathrm{fp}}\underset{n=1}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{(-1)}^n{J}_{2n}\left(2\mathrm{\&beta;}\right)\cos \left[2n({\mathrm{\&omega;}}_{\mathrm{sw}}t-{\mathrm{\&omega;}}_{\mathrm{sw}}{\mathrm{\&tau;}}_{\mathrm{fp}})\right]+$

$4R\sin {\mathrm{\&omega;}}_c{\mathrm{\&tau;}}_{\mathrm{fp}}\underset{n=1}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{(-1)}^n{J}_{2n+1}\left(2\mathrm{\&beta;}\right)\cos \left[(2n+1)({\mathrm{\&omega;}}_{\mathrm{sw}}t-{\mathrm{\&omega;}}_{\mathrm{sw}}{\mathrm{\&tau;}}_{\mathrm{fp}})\right]\}---\left(5\right)$

Get τ _Fp=0.5/f _Sw, and select ω _cAnd τ _FpMake cos ω _cτ _Fp=1, thus make the maximization of even-order harmonic composition, odd harmonic composition (2n+1) ω in the while erasure signal _Sw, this embodiment is 40GHz, so need to extract 8 order harmonic components, signal is reduced to:

$i_d\left(t\right)=\frac{i_0{A_o}^2{(1-R)}^2{m}_a[g\left(t\right)+{\cos \mathrm{\&omega;}}_{\mathrm{plt}}t]}{1+R^4-2{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="A20061011670100141.png"\; state="\{\{state\}\}">R</figure-callout>}}^2\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="A20061011670100141.png"\; state="\{\{state\}\}">cos</figure-callout>}2{\mathrm{\&omega;}}_c{\mathrm{\&tau;}}_{\mathrm{fp}}}\{D+4{\mathrm{RJ}}_8\left(2\mathrm{\&beta;}\right)\cos [8({\mathrm{\&omega;}}_{\mathrm{sw}}t-{\mathrm{\&omega;}}_{\mathrm{sw}}{\mathrm{\&tau;}}_{\mathrm{fp}})\left]\right\}$

Wherein D represents DC component, and D=1+R ²+ 2RJ ₀(2 β).

Amplifying splitter 3-2 with millimeter wave amplifies 17dB and is divided into two-way output the signal in 37.5GHz～40.5GHz frequency range, wherein to connect centre frequency be 40GHz, three dB bandwidth is the millimeter wave band pass filter 3-3 (1) of ± 200MHz in one tunnel output, the 40GHz millimeter wave carrier of baseband signal has been carried in taking-up, and its expression formula is:

$i_t\left(t\right)=\frac{4i_0{A_o}^2{A}_{e1}R{(1-R)}^2{m}_{a}g\left(t\right)}{1+R^4-2{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="A20061011670100141.png"\; state="\{\{state\}\}">R</figure-callout>}}^2\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="A20061011670100141.png"\; state="\{\{state\}\}">cos</figure-callout>}2{\mathrm{\&omega;}}_c{\mathrm{\&tau;}}_{\mathrm{fp}}}\&CenterDot;J_8\left(2\mathrm{\&beta;}\right)\cos \left[8({\mathrm{\&omega;}}_{\mathrm{sw}}t-{\mathrm{\&omega;}}_{\mathrm{sw}}{\mathrm{\&tau;}}_{\mathrm{fp}})\right]\}$

A wherein _E1Amplify the gain of splitter 3-2 for millimeter wave.

This signal sends through circulator 3-4 and antenna 3-5 again, has finished the descending function of signal.

It is that 38GHz, three dB bandwidth are the millimeter wave band pass filter 3-3 (2) of 40MHz that another road output of millimeter wave amplification splitter 3-2 connects centre frequency, takes out the millimeter wave reference local oscillator 3-7 of 38GHz, and its expression formula is:

$i_{\mathrm{ro}}\left(t\right)=\frac{2i_0{A_o}^2{A}_{e1}R{(1-R)}^2{m}_a}{1+R^4-2{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="A20061011670100141.png"\; state="\{\{state\}\}">R</figure-callout>}}^2\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="A20061011670100141.png"\; state="\{\{state\}\}">cos</figure-callout>}2{\mathrm{\&omega;}}_c{\mathrm{\&tau;}}_{\mathrm{fp}}}\&CenterDot;J_8\left(2\mathrm{\&beta;}\right)\cos [8({\mathrm{\&omega;}}_{\mathrm{sw}}t-{\mathrm{\&omega;}}_{\mathrm{sw}}{\mathrm{\&tau;}}_{\mathrm{fp}})-{\mathrm{\&omega;}}_{\mathrm{plt}}t]\}---\left(7\right)$

The key technology of up link is the generation of millimeter wave reference local oscillator 3-7 in the base station 3, has solved after this problem by said method, and the structure of up link becomes relative simple with signal processing:

The signal that base station 3 antenna 3-5 receive is the 40GHz millimeter-wave signal that is subjected to the modulation of user's uplink baseband information, this millimeter-wave signal is behind three end circulator 3-4, low noise amplifier 3-6, take out the intermediate frequency subcarrier of 2GHz by frequency mixer 3-9 and the frequency conversion of millimeter wave local oscillator 3-8 homodyne, with multiplication factor is that 40dB, centre frequency are 2GHz, bandwidth for the intermediate frequency filtering amplifier 3-9 of ± 200MHz amplifies the filtering of intermediate frequency subcarrier, makes its directly modulated laser 3-10; The up light wave that central station 3 receives obtains the intermediate frequency subcarrier through photo-detector 1-6 light-to-current inversion, and the local oscillator through intermediate frequency mixer 1-12 and 2GHz is down-converted to base band again, recovers user uplink baseband signal 1-14 with decision device 1-13 then.

Claims (2)

1. the transmitted in both directions structure based on insertion pilot tone system millimeter wave optical fibre transmission system constitutes uplink downlink by central station (1) and base station (3) by optical fiber bidirectional transmission link (2) interconnection, it is characterized in that:

1) structure of described down link is: the laser (1-1) in the central station (1) links to each other by tail optical fiber with a phase-modulator (1-2), a frequency sweep sine-wave oscillator (1-6) is connected to the input of a microwave amplifier (1-7) by electric lead, the output of microwave amplifier (1-7) connects the control electrode of described phase-modulator (1-2) by electric lead, the output of phase-modulator (1-2) connects an intensity modulator (1-3) by tail optical fiber, there are a pilot oscillator (1-8) and downgoing baseband signal (1-10) to be connected to two inputs of a wave multiplexer (1-9) respectively by electric lead, the output of wave multiplexer (1-9) connects the control electrode of described intensity modulator (1-3) by electric lead, the output of intensity modulator (1-3) connects a Fabry-Perot optical filter (1-4) by tail optical fiber, the output of Fabry-Perot optical filter (1-4) connects an erbium-doped fiber amplifier EDFA (1-5) by tail optical fiber, and the output of erbium-doped fiber amplifier EDFA (1-5) is connected to described optical fiber bidirectional transmission link (2) by tail optical fiber; The terminal input that in base station (3), connects a photo-detector (3-1) of described optical fiber bidirectional transmission link (2), the output of photo-detector (3-1) connects the input that a millimeter wave amplifies splitter (3-2) by electric lead, millimeter wave amplifies the input of one road output of splitter (3-2) by an electric lead millimeter wave band pass filter of connection (3-3 (1)), the output of millimeter wave band pass filter (3-3 (1)) connects the port one of one three end circulator (3-4) by electric lead, the port 2 of three end circulators (3-4) connects antenna (3-5) by feeder line, millimeter-wave signal is launched through antenna (3-5), thereby realizes the downlink transfer function of signal; Other one road output of millimeter wave amplification splitter (3-2) connects the input of another millimeter wave band pass filter (3-3 (2)), output at this millimeter wave band pass filter (3-3 (2)) obtains millimeter wave reference local oscillator (3-7), for the uplink signal transmission provides the down-conversion reference local oscillator;

2) structure of described up link is: the subscriber signal that the antenna (3-5) in base station (3) is gathered enters described three end circulator (3-4) ports 2 by feeder line, by 3 outputs of three end circulator (3-4) ports, three end circulator (3-4) ports 3 connect the input of a low noise amplifier (3-6) by electric lead, low noise amplifier (3-6) output connects an input of a millimeter wave mixer (3-8) by electric lead, the millimeter wave reference local oscillator (3-7) of the output output of described millimeter wave band pass filter (3-3 (2)) is added to another input of millimeter wave mixer (3-8) by electric lead, the output of millimeter wave mixer (3-8) connects the input of an intermediate frequency filtering amplifier (3-9) by electric lead, the output of intermediate frequency filtering amplifier (3-9) is by the input of an electric lead laser of connection (3-10), and the light wave of this laser (3-10) output connects optical fiber bidirectional transmission link (2) by tail optical fiber; In central station (1), the input of a photo-detector (1-11) connects described optical fiber bidirectional transmission link (2), the output of this photo-detector (1-11) is connected to an input of intermediate frequency mixer (1-12) by electric lead, another input of intermediate frequency mixer (1-12) connects the output of pilot oscillator (1-8) by electric lead, the output of intermediate frequency mixer (1-12) is directly exported user uplink baseband signal (1-14) by the input of an electric lead decision device of connection (1-13) at decision device (1-13).

2. the two-way signaling transmission method based on insertion pilot tone system millimeter wave optical fibre transmission system adopts the up-down bidirectional transmission structure of the described millimeter wave optical fibre transmission system of claim 1 to carry out the two-way signaling transmission, it is characterized in that:

1) downstream signal transmission method: with the frequency sweep sine wave light wave is carried out phase modulated at central station (1), mixed signal with downgoing baseband signal and pilot tone sine wave is carried out intensity modulated to light wave, and with Fabry-Perot optical filter (1-4) light wave of intensity and Phase Double remodulates is carried out filtering and produce pectination spectrum; In the base station (3), the light wave that comes from central station (1) transmission carries out light-to-current inversion by photo-detector (3-1), amplifying splitter (3-2) with millimeter wave then amplifies the signal after the light-to-current inversion and is divided into two-way, allow it respectively by two different millimeter wave band pass filters (3-3 (1) then, (2)), and obtain descending modulated wave of millimeter wave and millimeter wave reference local oscillator (3-7) respectively, the descending modulated wave of millimeter wave is launched by antenna (3-5) through amplifying the back, thereby realize the downstream signal transfer function, also provide millimeter wave reference local oscillator (3-7) simultaneously for uplink signal transmissions;

2) uplink signal transmission method: user's millimeter wave upward signal that base station (3) receive from antenna (3-5) is after low noise amplifier (3-6) amplifies, in frequency mixer (3-8) with described millimeter wave reference local oscillator (3-7) mixing, realize the down-conversion of signal, acquisition is subjected to the intermediate frequency subcarrier of uplink baseband signal modulation, with the direct modulated laser of intermediate frequency subcarrier (3-10), its output is transferred to the photo-detector (1-11) of central station (1), output intermediate frequency subcarrier after light-to-current inversion, pass through down-conversion again, decision device output user uplink baseband signal (1-14), thus realize the uplink signal transmissions function.

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