CN109379141B - Time division duplex radio over fiber transmission system - Google Patents
Time division duplex radio over fiber transmission system Download PDFInfo
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- CN109379141B CN109379141B CN201811394271.4A CN201811394271A CN109379141B CN 109379141 B CN109379141 B CN 109379141B CN 201811394271 A CN201811394271 A CN 201811394271A CN 109379141 B CN109379141 B CN 109379141B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/40—Transceivers
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/25—Arrangements specific to fibre transmission
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L5/00—Arrangements affording multiple use of the transmission path
- H04L5/14—Two-way operation using the same type of signal, i.e. duplex
- H04L5/1469—Two-way operation using the same type of signal, i.e. duplex using time-sharing
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Abstract
The invention discloses a time division duplex radio over fiber transmission system, which comprises an access point for accessing time division duplex mode signals, a near-end optical module, a far-end optical module, an analog optical fiber line for transmitting optical signals between the near-end optical module and the far-end optical module, and an antenna for receiving and transmitting the time division duplex mode signals, wherein the near-end optical module is used for receiving the time division duplex mode signals; the near-end optical module is used for realizing control of a downlink optical link and distribution and transmission of uplink and downlink signals, and realizing electro-optical conversion of downlink electric signals and photoelectric conversion of uplink optical signals; the far-end optical module is used for being matched with the near-end optical module to realize control of an uplink and distribution and transmission of uplink and downlink signals, photoelectric conversion of the downlink optical signals and electro-optical conversion of uplink electric signals, and amplification processing of radio-frequency signals. The invention realizes effective isolation between the uplink and the downlink by controlling the on-off of the optical link, reduces the devices of the far-end optical module, reduces the volume and greatly increases the reliability of the far-end optical module.
Description
Technical Field
The invention relates to the field of network communication, in particular to a time division duplex radio over fiber transmission system.
Background
With the rapid development of communication technology, the coverage range of WiFi and mobile communication is wider and wider, and since the construction cost of a base station is huge, the complexity is high, and the maintenance is difficult, the radio over fiber technology is brought forward. The radio over fiber system realizes long-distance transmission by utilizing the advantages of long transmission distance, small attenuation, good anti-interference performance and the like of the optical fiber; meanwhile, the remote node only needs to complete the functions of power amplification, optical/electrical conversion and electrical/optical conversion, the functions and the structure are simpler, the cost and the maintenance difficulty can be effectively reduced, and the reliability of the system is improved.
When the radio over fiber technology is applied to the time division duplex transmission mode, the uplink and the downlink work at the same frequency, and the transceiving operation is performed by allocating different time slots. If the isolation between the uplink and the downlink is not enough, the uplink and the downlink are easy to form a loop, signals in the uplink (or the downlink) return to the uplink (or the downlink) through the loop again, and the signals in the original link are interfered after being amplified by the amplifier; in addition, signals passing through the downlink remote node power amplifier are prone to leak into the uplink, resulting in damage to the low noise amplifier in the uplink due to excessive input power.
Radio over fiber systems and mobile communication systems usually employ integrated single-pole double-throw switches or passive ferrite circulators for switching the transceiver circuits and isolating the uplink and downlink. The former needs an additional control circuit for judging the uplink and downlink of signals, which increases the complexity of the structure of the remote unit and leads to the increase of cost if a high-isolation switch is adopted; the latter circuit is simple, but has limited isolation, large volume and relatively high price. In addition, the additional introduction of attenuators and amplifiers is also used to improve the isolation of the link, which increases the complexity and cost of the circuitry and reduces the reliability of the remote unit.
How to improve the isolation between the uplink and downlink in the tdd optical wireless system, further improve the reliability of the remote node, reduce the maintenance difficulty of the remote unit, and reduce the system cost is a problem that needs to be solved.
Disclosure of Invention
The invention provides a time division duplex radio over fiber transmission system, which aims to solve the problems of small isolation between an uplink and a downlink in the time division duplex radio over fiber system and high maintenance difficulty.
In order to achieve the purpose of the invention, the technical scheme is as follows: a time division duplex radio over fiber transmission system comprises an access point for accessing time division duplex mode signals, a near-end optical module, a far-end optical module, an analog optical fiber line for transmitting optical signals between the near-end optical module and the far-end optical module, and an antenna for receiving and transmitting the time division duplex mode signals;
the near-end optical module is used for realizing control of a downlink optical link and distribution and transmission of uplink and downlink signals, and realizing electro-optical conversion of downlink electric signals and photoelectric conversion of uplink optical signals;
the far-end optical module is used for being matched with the near-end optical module to realize control of an uplink and distribution and transmission of uplink and downlink signals, photoelectric conversion of the downlink optical signals and electro-optical conversion of uplink electric signals, and amplification processing of radio-frequency signals.
Preferably, the near-end optical module includes a near-end signal control module, a near-end switch for performing uplink and downlink signal distribution, a near-end laser for converting a downlink signal output by the near-end switch from an electrical signal form to an optical signal, and a near-end detector for converting an uplink signal transmitted by the analog optical fiber line from an optical signal form to an electrical signal; the analog optical fiber line comprises an uplink analog optical fiber line and a downlink analog optical fiber line;
one end of the near-end signal control module is externally connected with an access point for time division duplex mode signal access, and the other end of the near-end signal control module is respectively connected with the input end of the near-end laser and the output end of the near-end detector through a near-end switch; the near-end signal control module outputs two paths of control signals, one path is used for controlling a near-end switch, and the other path is used for controlling a near-end laser; the output end of the near-end laser is connected with the far-end optical module through a downlink analog optical fiber line; and the input end of the near-end detector is connected with the far-end optical module through an analog optical fiber line of an uplink.
Further, the near-end signal control module comprises a coupler, a detector, a near-end comparator and a near-end optical power constant circuit; the access point, the coupler, the detector, the near-end comparator, the near-end optical power constant circuit and the near-end laser are sequentially and electrically connected, and the near-end switch is respectively and electrically connected with the coupler and the near-end comparator;
the coupler is used for shunting an input radio frequency signal, a signal output by the straight-through end is loaded to the near-end switch, and an output signal of the coupler is used for voltage detection;
the wave detector is used for detecting the signal output by the coupling end of the coupler and converting the signal from an alternating current signal into a direct current signal;
the near-end comparator is used for comparing the voltage of the direct-current signal output by the detector with the voltage arranged in the comparator to generate a detection signal;
the near-end optical power constant circuit controls the working state of the near-end laser according to the detection signal generated by the near-end comparator, and stabilizes the optical power of the laser at the same time.
Preferably, the far-end optical module comprises a far-end detector, a far-end signal control module, a far-end laser, a power amplifier, a low noise amplifier and a far-end switch;
the analog optical fiber line comprises an uplink analog optical fiber line and a downlink analog optical fiber line, the input end of the far-end detector is connected with the output end of the near-end optical module through the downlink analog optical fiber line, and the output end of the far-end detector is connected with the far-end switch through the power amplifier; the far-end detector is used for converting a downlink signal transmitted by the analog optical fiber line into an electric signal in an optical signal form;
the remote switch is externally connected with an antenna and is simultaneously connected with the output end of the power amplifier and the input end of the low-noise amplifier respectively; the remote switch is used for exchanging uplink and downlink signals;
the output end of the low-noise amplifier is connected with the input end of the far-end laser and is used for amplifying the uplink signal output by the far-end switch;
the output end of the far-end laser is connected with the input end of the near-end optical module through an analog optical fiber line of an uplink, and the far-end laser is used for converting an uplink signal in an electric signal form into an optical signal;
the detection end of the far-end signal control module is used for being connected with a far-end detector and outputting two paths of control signal ends at the same time, one end of the far-end signal control module is used for controlling a far-end switch, and the other end of the far-end signal control module is used for controlling a far-end laser; the far-end signal control module is used for matching with the near-end optical module, judging the uplink and downlink of signals, controlling the on-off of an uplink optical link and controlling the conducting direction of a far-end switch.
Furthermore, the far-end signal control module comprises an indicator light circuit, a far-end comparator and a far-end optical power constant circuit; the far-end detector, the indicator light circuit, the far-end comparator, the far-end optical power constant circuit and the far-end laser are sequentially and electrically connected, and the far-end switch is connected with the far-end comparator;
the indicating lamp circuit is connected with the far-end detector, outputs a corresponding voltage signal according to the working state of the detector and simultaneously indicates whether the far-end detector receives an optical signal;
the far-end comparator is used for receiving the voltage signal provided by the indicator light circuit, comparing the voltage signal with the built-in voltage of the far-end comparator and generating control voltage to control the far-end optical power constant circuit and the far-end switch;
the far-end optical power constant circuit controls the working state of the far-end laser according to the detection signal generated by the comparator, and simultaneously stabilizes the optical power of the far-end laser.
Further, the indicating lamp circuit comprises NPN triodes Q1 and Q2, resistors R1, R2, R3 and R4 and a light emitting diode LED;
the far-end detector is connected with a base electrode of an NPN triode Q1, an emitting electrode of the NPN triode Q1 is grounded through a resistor R2, a collector electrode of the NPN triode Q1 is connected with VCC through a resistor R1, and meanwhile a collector electrode of the NPN triode Q1 is connected with a base electrode of an NPN triode Q2;
an emitter of the NPN triode Q2 is grounded through a resistor R4, and a collector of the NPN triode Q2 is connected with a negative electrode of the light emitting diode LED; the anode of the LED is connected with VCC through a resistor R3;
the input end of the far-end comparator is connected between the base electrode of the NPN triode Q2 and the collector electrode of the NPN triode Q1.
Preferably, the near-end signal control module, the near-end laser, the near-end switch, the far-end detector, the far-end signal control module, the far-end laser, and the far-end switch form a control path of the uplink and downlink optical link.
Furthermore, the near-end switch and the far-end switch both adopt radio frequency switches.
Further, when the optical fiber link is in a transmitting state, a near-end laser in the near-end optical module outputs an optical signal; the remote signal control module detects that the remote detector receives an optical signal, and controls the remote switch to switch on the power amplifier, namely, the downlink is switched on; meanwhile, the remote signal control module controls the remote laser to enable the remote laser to have no optical signal output, and the uplink is disconnected.
Further, when the optical fiber link is in a receiving state, the near-end laser in the near-end optical module does not output optical signals, that is, a downlink is disconnected; when the far-end detector does not receive the optical signal, the far-end signal control module controls the far-end laser to output the optical signal, and simultaneously controls the far-end switch to switch on the low-noise amplifier, so that the uplink is conducted.
The invention has the following beneficial effects: the invention skillfully designs the near-end signal control module and the far-end signal control module, and the near-end signal control module, the near-end laser, the far-end detector, the far-end signal control module, the far-end laser and the far-end switch form a control path of an uplink optical link and a downlink optical link, thereby controlling the working states of the uplink laser and the downlink laser, solving the problem of limited isolation between the uplink and the downlink in the existing radio over fiber system, simplifying the far-end node, increasing the reliability of the far-end node and reducing the system cost.
Drawings
Fig. 1 is a block diagram of the time division duplex radio over fiber transmission system of the present invention.
Fig. 2 is a block diagram of a near-end signal control module in fig. 1.
Fig. 3 is a block diagram of a remote signal control module in fig. 1.
Fig. 4 is a schematic circuit diagram of the indicator lamp circuit of fig. 3.
Fig. 5 is a flow chart of the operation of the control signal in the downlink of the signal of fig. 1.
Fig. 6 is a flowchart of the operation of the control signal in the uplink of the signal in fig. 1.
Detailed Description
The invention is described in detail below with reference to the drawings and the detailed description.
Example 1
As shown in fig. 1, a time division duplex radio over fiber transmission system includes an access point 100 for time division duplex mode signal access, a near-end optical module 101, a far-end optical module 103, an analog optical fiber line 102 for transmitting an optical signal between the near-end optical module and the far-end optical module, and an antenna 104 for transceiving a time division duplex mode signal.
The access point 100 for time division duplex mode signal access is externally connected with a WiFi signal and a TD-LTE 4G signal.
The near-end optical module 101 is configured to implement control of a downlink optical link and distribution and transmission of uplink and downlink signals, and implement electrical-to-optical conversion of a downlink electrical signal and optical-to-electrical conversion of an uplink optical signal;
the far-end optical module 103 is used for being matched with the near-end optical module 101 to realize uplink control and uplink and downlink signal distribution transmission, realize photoelectric conversion of downlink optical signals and electro-optical conversion of uplink electric signals, and realize amplification processing of radio-frequency signals.
The analog optical fiber line 102 includes an upstream optical fiber line and a downstream optical fiber line.
The near-end optical module 101 of this embodiment includes a near-end signal control module 111, a near-end switch 112 for performing uplink and downlink signal distribution, a near-end laser 113 for converting a downlink signal output by the near-end switch 112 into an optical signal in an electrical signal form, and a near-end detector 114 for converting an uplink signal transmitted by an optical fiber into an electrical signal in an optical signal form; the output end of the access point 100 for time division duplex mode signal access is connected with the input end of the near-end signal control module 111; the near-end signal control module 111 outputs two paths of control signals, one path is used for controlling the near-end switch 112, the other path is used for controlling the near-end laser 113, and the near-end control module 111 is used for realizing the judgment of signal uplink or downlink and the on-off control of a downlink optical link; the near-end switch 112 has three ports, wherein port 1 is an input port, and port 2 and port 3 are output ports; the output end of the near-end signal control module 111 is connected 114 with a near-end laser 113 and a near-end detector through a near-end switch 112; the near-end switch 112 is a radio frequency switch chip.
The near-end signal control module 111 controls the working state of the near-end laser 113 by detecting the input transmitting signal power and generating a control signal. The near-end switch 112 in the near-end optical module 101 realizes the distributed transmission of uplink and downlink signals.
The near-end optical module 101 is configured to implement control of a downlink optical link and distribution and transmission of uplink and downlink signals, and implement electrical-to-optical conversion of electrical signals and optical-to-electrical conversion of optical signals.
In this embodiment, a signal transmitted from the near-end signal control module 111 in the near-end optical module 101 to the near-end switch 112 is output through the port 2 of the near-end switch 112, and then is loaded onto the near-end laser 113, so that conversion from an electrical signal to an optical signal is realized, and the signal is transmitted to the far-end optical module 103 through the downlink optical fiber line 102.
As shown in fig. 2, the near-end signal control module 111 includes a coupler 201, a detector 202, a near-end comparator 203, a near-end optical power constant circuit 204; the access point 100, the coupler 201, the detector 202, the near-end comparator 203, the near-end optical power constant circuit 204 and the near-end laser 113 are electrically connected in sequence, and the near-end switch 112 is electrically connected with the coupler 201 and the near-end comparator 203 respectively;
the coupler 201 is a four-port element with one port grounded. When the port 1 is used as an input end, the port 2 is a straight-through end thereof, and the port 3 is a coupling end thereof; when port 2 is the input port, port 1 is its pass-through port and port 3 is its isolation port. The coupler 201 is used for splitting an input radio frequency signal, a signal output by the through terminal is loaded to the near-end switch 112, and an output signal of the coupler 201 is used for voltage detection;
the detector 202 is configured to detect a signal output by the coupling end of the coupler 201, and convert the signal from an ac signal to a dc signal;
the near-end comparator 203 is configured to compare the voltage of the dc signal output by the detector 202 with a voltage set in the near-end comparator 203 to generate a detection signal;
the near-end optical power constant circuit 204 controls the operating state of the near-end laser 113 according to the detection signal generated by the near-end comparator 203, and stabilizes the optical power of the laser.
In the embodiment, the coupler 201 divides the radio frequency signal input from the port 1 into two paths, one path is loaded to the near-end switch 112 from the through port 3, and the other path is distributed to the detector 202 from the coupling port 2; and on the other hand, the uplink radio frequency signal input from the port 3 is transmitted to the port 1. The detector 202 receives the rf ac signal output from port 2 of the coupler 201 and converts it into a dc signal. The reference voltage is set in the near-end comparator 203, and the signal voltage output by the detector 202 is compared with the reference voltage to generate a corresponding control voltage to control the conduction direction of the near-end switch 112 and the working state of the near-end optical power constant circuit 204, so as to control whether the near-end laser 113 generates an optical signal.
As shown in fig. 1, the far-end optical module 103 in this embodiment includes a far-end detector 121 for converting a downlink signal transmitted by an optical fiber from an optical signal form to an electrical signal, a far-end signal control module 122, a far-end laser 123 for converting an uplink signal from an electrical signal form to an optical signal, a power amplifier 124 for amplifying the downlink signal, a low-noise amplifier 125 for amplifying the uplink signal output by the far-end switch, and a far-end switch 126 for exchanging uplink and downlink signals, where the far-end switch 126 is a radio frequency switch.
The input end of the far-end detector 121 is connected with the output end of the near-end laser 113 through a downlink optical fiber line in the analog optical fiber line 102, and the output end of the far-end detector 121 is connected with the input end of the far-end switch 126 through the power amplifier 124; the output end of the far-end laser 123 is connected with the input end of the near-end detector 114 through an uplink optical fiber line in the analog optical fiber line 102, and the input end of the far-end laser 123 is connected with the output end of the far-end switch 126 through a low-noise amplifier 125; the other output end of the remote switch 126 is connected with the antenna 104; the remote signal control module 122 outputs two control signals, one of which is transmitted to the remote switch 126, and the other is used for controlling the remote laser 123, and meanwhile, the remote signal control module 122 is connected with the remote detector 121.
The far-end signal control module 122 is configured to cooperate with the near-end optical module 101 to determine uplink and downlink of a signal, control on/off of an uplink optical link, and control a conduction direction of the far-end switch 126; the far-end optical module 103 is used for realizing uplink control and uplink and downlink signal distribution transmission by matching with the near-end optical module 101, realizing photoelectric conversion of optical signals and electro-optical conversion of electrical signals, and realizing amplification processing of radio-frequency signals.
The remote signal control module 122 detects whether the remote detector 121 receives the optical signal, and generates a control signal to control the operating states of the remote laser 123 and the remote switch 126. When the far-end detector 121 receives the optical signal, the far-end signal control module 122 controls the far-end laser 123 to have no optical signal output, and the far-end switch 126 is turned on and goes down; when the far-end detector 121 does not receive the optical signal, the far-end laser 123 outputs the optical signal, and the far-end switch 126 is turned on to go up. When the signal is down, the up optical link is disconnected and no light is output; on the contrary, when the signal goes up, the down optical link is disconnected and there is optical output.
The remote switch 126 in the remote optical module 103 divides the radio frequency signal into a downlink channel and an uplink channel. The power amplifier 124 amplifies the downlink signal output by the remote detector 121, and the low noise amplifier 125 amplifies the uplink signal received by the antenna. The near-end detector 114 and the far-end detector 121 are both configured with photoelectric conversion modules for realizing photoelectric conversion; the near-end laser 113 and the far-end laser 123 are both configured with an electro-optical conversion module for realizing electro-optical conversion.
As shown in fig. 3, the remote signal control module 122 of this embodiment includes an indicator light circuit 301, a remote comparator 302, and a remote optical power constant circuit 303;
the indicator light circuit 301 is connected to the remote detector 121, and outputs a corresponding voltage signal according to the working state of the remote detector 121, and indicates whether the remote detector 121 receives an optical signal;
the remote comparator 302 is configured to receive a voltage signal provided by the indicator lamp circuit 301, compare the voltage signal with an internal voltage of the remote comparator 302, and generate a control voltage to control the remote optical power constant circuit 303 and the remote switch 126;
the far-end optical power constant circuit 303 controls the operating state of the near-end laser 113 according to the detection signal generated by the far-end comparator 302, and stabilizes the optical power of the laser.
In this embodiment, when the remote detector 121 receives the optical signal, the indicator light circuit 301 emits an indicator light, and provides a control voltage to the remote comparator 302. The reference voltage is set in the remote comparator 302, and the voltage output by the indicator lamp circuit 301 is compared with the reference voltage to generate a corresponding control voltage to control the working states of the remote optical power constant circuit 303 and the remote switch 126.
As shown in fig. 4, the indicator light circuit 301 includes NPN transistors Q1, Q2, resistors R1, R2, R3, R4, and a light emitting diode LED; the resistance value of the resistor R1 is higher than the resistance values of the resistors R2, R3, and R4.
The far-end detector 121 is connected with a base electrode of an NPN triode Q1, an emitting electrode of the NPN triode Q1 is grounded through a resistor R2, a collector electrode of the NPN triode Q1 is connected with VCC through a resistor R1, and a collector electrode of the NPN triode Q1 is connected with a base electrode of an NPN triode Q2;
an emitter of the NPN triode Q2 is grounded through a resistor R4, and a collector of the NPN triode Q2 is connected with a negative electrode of the light emitting diode LED; the anode of the LED is connected with VCC through a resistor R3;
the input of the remote comparator 302 is connected between the base of the NPN transistor Q2 and the collector of the NPN transistor Q1.
When the far-end detector 121 outputs an electric signal, the triode Q1 is turned on, and since the resistance value of the R1 is much larger than that of the R2, the voltage at the point P is close to 0, at this time, the triode Q2 is turned off, and no current passes through the light emitting diode LED, so that the light emitting diode LED is in an off state. When no electrical signal is output from the remote detector 121, the transistor Q1 is turned off, the current of R1 flows to point P, the voltage at point P rises, and at this time, the transistor Q2 is turned on, and the light emitting diode has current flowing through it and is in a light emitting state.
Since the level value of the point P changes with the output of the remote detector 121, connecting the point P to the remote comparator 302 allows the output change of the remote detector 121 to affect the output level of the remote comparator 302 for controlling the remote laser 123 and the remote switch 126.
In this embodiment, the near-end signal control module 111, the near-end laser 113, the near-end switch 112, the far-end detector 121, the far-end signal control module 122, the far-end laser 123, and the far-end switch 126 form a control path of an uplink and a downlink optical link.
When the optical fiber link is in a transmitting state, the near-end laser 113 in the near-end optical module 101 outputs an optical signal, the far-end signal control module 122 detects that the far-end detector 121 receives the optical signal, and the far-end signal controller module 122 controls the far-end switch 126 to switch on the power amplifier, that is, the downlink is switched on; meanwhile, the remote signal control module 122 controls the remote laser 123 to make it have no light signal output and the uplink optical fiber line is disconnected.
When the optical fiber link is in a receiving state, the near-end laser 113 in the near-end optical module 101 has no optical signal output, that is, the downlink optical fiber line is disconnected; meanwhile, when the remote detector 121 does not receive the optical signal, the remote signal control module 122 controls the remote laser 123 to output the optical signal, and controls the remote switch 126 to turn on the low noise amplifier 125, so that the uplink is turned on.
As shown in fig. 5, the working flow chart of the control signal when the signal goes down. The radio frequency signal that descends from the coupler 201 to the far-end switch 126, wherein a part of the radio frequency signal enters the detector 202 through the port 2 of the coupler 201, the detector 202 converts the input radio frequency signal from an alternating current signal to a direct current signal, and loads the direct current signal to the near-end comparator 203, the near-end comparator 203 checks that the voltage of the direct current signal is greater than a reference value, outputs a high-level voltage signal, controls the near-end switch 112 to be turned on and descend, and controls the near-end optical power constant circuit 204 to operate, and then excites the near-end laser 113 to operate, converts the radio frequency signal input by the near-end switch 112 to an optical signal, and then transmits the optical signal to the far-end. The far-end detector 121 receives the downlink signal in the form of the optical signal, converts the downlink signal into an electrical signal, and simultaneously indicates that the P point of the lamp circuit 301 is at a low level, and inputs the electrical signal to the far-end comparator 302, and the far-end comparator 302 detects that the voltage is lower than an internal reference voltage to generate a low-level voltage signal, so as to control the far-end switch 126 to be turned on and down, and simultaneously control the far-end optical power constant circuit 303 to be not operated, so as to control the far-end laser 123 to have no optical signal output, and the uplink optical link. Therefore, when a signal is input into the port 1 of the coupler 201, the control circuit controls the downlink to be connected and normally work, and controls the uplink optical path to be disconnected.
As shown in fig. 6, a working flow chart of a control signal during signal uplink, when a signal is uplink, no signal is input at port 1 of the coupler 201, the voltage of the dc signal output by the detector 202 is at a low level and is applied to the near-end comparator 203, the near-end comparator 203 checks that the voltage of the dc signal is smaller than a reference value, and outputs a low-level voltage signal, controls the near-end switch 112 to turn on uplink, controls the near-end optical power constant circuit 204 to not operate, controls the near-end laser 113 to have no optical signal output, and turns off the downlink. The far-end detector 121 does not receive the optical signal, affects the point P of the indicator light circuit 301 to generate a high level, inputs the high level to the far-end comparator 302, the far-end comparator 302 detects that the voltage is higher than an internal reference voltage, outputs a high-level voltage signal, controls the far-end switch 126 to be conducted and uplink, controls the far-end optical power constant circuit 303 to work, further controls the far-end laser 123 to convert the radio-frequency signal output by the low-noise amplifier 125 into an optical signal from an electrical signal, and transmits the optical signal to the near-end detector 114 through the optical fiber 101, and the uplink is connected. Therefore, when no signal is input into port 1 of coupler 201, the control circuit controls the uplink to be connected and normally work, and simultaneously controls the downlink optical path to be disconnected.
It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.
Claims (2)
1. A time division duplex radio over fiber transmission system, comprising: the system comprises an access point for accessing time division duplex mode signals, a near-end optical module, a far-end optical module, an analog optical fiber line for transmitting optical signals between the near-end optical module and the far-end optical module, and an antenna for receiving and transmitting the time division duplex mode signals;
the near-end optical module is used for realizing control of a downlink optical link and distribution and transmission of uplink and downlink signals, and realizing electro-optical conversion of downlink electric signals and photoelectric conversion of uplink optical signals;
the far-end optical module is used for being matched with the near-end optical module to realize control of an uplink and distribution and transmission of uplink and downlink signals, photoelectric conversion of the downlink optical signals and electro-optical conversion of uplink electric signals, and amplification processing of radio-frequency signals;
the near-end optical module comprises a near-end signal control module, a near-end switch for distributing uplink and downlink signals, a near-end laser for converting the downlink signals output by the near-end switch into optical signals in an electrical signal form, and a near-end detector for converting the uplink signals transmitted by the analog optical fiber line into the electrical signals in an optical signal form; the analog optical fiber line comprises an uplink analog optical fiber line and a downlink analog optical fiber line;
one end of the near-end signal control module is externally connected with an access point for time division duplex mode signal access, and the other end of the near-end signal control module is respectively connected with the input end of the near-end laser and the output end of the near-end detector through a near-end switch; the near-end signal control module outputs two paths of control signals, one path is used for controlling a near-end switch, and the other path is used for controlling a near-end laser; the output end of the near-end laser is connected with the far-end optical module through a downlink analog optical fiber line; the input end of the near-end detector is connected with the far-end optical module through an analog optical fiber line of an uplink;
the near-end signal control module comprises a coupler, a detector, a near-end comparator and a near-end optical power constant circuit; the access point, the coupler, the detector, the near-end comparator, the near-end optical power constant circuit and the near-end laser are sequentially and electrically connected, and the near-end switch is respectively and electrically connected with the coupler and the near-end comparator;
the coupler is used for shunting an input radio frequency signal, a signal output by the straight-through end is loaded to the near-end switch, and an output signal of the coupler is used for voltage detection;
the wave detector is used for detecting the signal output by the coupling end of the coupler and converting the signal from an alternating current signal into a direct current signal;
the near-end comparator is used for comparing the voltage of the direct-current signal output by the detector with the voltage arranged in the comparator to generate a detection signal;
the near-end optical power constant circuit controls the working state of the near-end laser according to the detection signal generated by the near-end comparator, and stabilizes the optical power of the near-end laser;
the remote optical module comprises a remote detector, a remote signal control module, a remote laser, a power amplifier, a low-noise amplifier and a remote switch;
the analog optical fiber line comprises an uplink analog optical fiber line and a downlink analog optical fiber line, the input end of the far-end detector is connected with the output end of the near-end optical module through the downlink analog optical fiber line, and the output end of the far-end detector is connected with the far-end switch through the power amplifier; the far-end detector is used for converting a downlink signal transmitted by the analog optical fiber line into an electric signal in an optical signal form;
the remote switch is externally connected with an antenna and is simultaneously connected with the output end of the power amplifier and the input end of the low-noise amplifier respectively; the remote switch is used for exchanging uplink and downlink signals;
the output end of the low-noise amplifier is connected with the input end of the far-end laser and is used for amplifying the uplink signal output by the far-end switch;
the output end of the far-end laser is connected with the input end of the near-end optical module through an analog optical fiber line of an uplink, and the far-end laser is used for converting an uplink signal in an electric signal form into an optical signal;
the detection end of the far-end signal control module is used for being connected with a far-end detector and outputting two paths of control signal ends at the same time, one end of the far-end signal control module is used for controlling a far-end switch, and the other end of the far-end signal control module is used for controlling a far-end laser; the far-end signal control module is used for matching with the near-end optical module, judging the uplink and downlink of signals, controlling the on-off of an uplink optical link and controlling the conducting direction of a far-end switch;
the far-end signal control module comprises an indicator light circuit, a far-end comparator and a far-end optical power constant circuit; the far-end detector, the indicator light circuit, the far-end comparator, the far-end optical power constant circuit and the far-end laser are sequentially and electrically connected, and the far-end switch is connected with the far-end comparator;
the indicating lamp circuit is connected with the far-end detector, outputs a corresponding voltage signal according to the working state of the detector and simultaneously indicates whether the far-end detector receives an optical signal;
the far-end comparator is used for receiving the voltage signal provided by the indicator light circuit, comparing the voltage signal with the built-in voltage of the far-end comparator and generating control voltage to control the far-end optical power constant circuit and the far-end switch;
the far-end optical power constant circuit controls the working state of the far-end laser according to the detection signal generated by the far-end comparator, and simultaneously stabilizes the optical power of the far-end laser;
the near-end signal control module, the near-end laser, the near-end switch, the far-end detector, the far-end signal control module, the far-end laser and the far-end switch form a control path of an uplink optical link and a downlink optical link;
the near-end switch and the far-end switch both adopt radio frequency switches;
when the optical fiber link is in a transmitting state, a near-end laser in the near-end optical module outputs an optical signal; the remote signal control module detects that the remote detector receives an optical signal, and controls the remote switch to switch on the power amplifier, namely, the downlink is switched on; meanwhile, the remote signal control module controls the remote laser to enable the remote laser to have no optical signal output and an uplink to be disconnected;
when the optical fiber link is in a receiving state, a near-end laser in the near-end optical module does not output optical signals, namely a downlink is disconnected; when the far-end detector does not receive the optical signal, the far-end signal control module controls the far-end laser to output the optical signal, and simultaneously controls the far-end switch to switch on the low-noise amplifier, so that the uplink is conducted.
2. The tdd radio-over-fiber transmission system according to claim 1, wherein: the indicating lamp circuit comprises NPN triodes Q1 and Q2, resistors R1, R2, R3 and R4 and a light emitting diode LED;
the far-end detector is connected with a base electrode of an NPN triode Q1, an emitting electrode of the NPN triode Q1 is grounded through a resistor R2, a collector electrode of the NPN triode Q1 is connected with VCC through a resistor R1, and meanwhile a collector electrode of the NPN triode Q1 is connected with a base electrode of an NPN triode Q2;
an emitter of the NPN triode Q2 is grounded through a resistor R4, and a collector of the NPN triode Q2 is connected with a negative electrode of the light emitting diode LED; the anode of the LED is connected with VCC through a resistor R3;
the input end of the far-end comparator is connected between the base electrode of the NPN triode Q2 and the collector electrode of the NPN triode Q1.
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| CN112751617B (en) * | 2019-10-31 | 2022-05-20 | Oppo广东移动通信有限公司 | Electronic setting, control method and device thereof, and storage medium |
| CN115483982B (en) * | 2022-08-30 | 2024-06-21 | 西北核技术研究所 | Analog optical link input signal measuring method and device |
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| CN101557253B (en) * | 2008-04-09 | 2012-07-18 | 邦讯技术股份有限公司 | TD-SCDMA fiber optic repeater and method for processing uplink and downlink of signals |
| CN201523385U (en) * | 2009-10-29 | 2010-07-07 | 天津七一二通信广播有限公司 | Fiber optic repeater compatible with homogeneous frequency mode and heterogeneous frequency mode |
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