JPH03502869A - Signal strength control system in optical fiber communication system - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Background of the invention of signal strength control system in optical fiber communication system Field of application of invention FIELD OF THE INVENTION This invention relates to fiber optic communication systems. In particular, this invention can measure signal strength in a communication system. The invention relates to a feedback control system that regulates within the range of a stem.

Although the invention will be described with reference to a particular implementation, the invention is not limited to this example. It's not something you can do. Those skilled in the art and those who can understand this description will understand that it is beyond the scope of this invention. Obviously, other embodiments can easily be envisaged.

Description of prior art In a fiber optic guidance system, the guided vehicle and Communication is improved through a fiber optic double pull between the vehicle and the control station. can do. Optical fiber is typically wound on a bobbin or as it travels along the path, it is secured by means capable of supplying the fiber.

In a wound optical fiber, the propagating energy of light is Divergence results in attenuation. This radiation loss caused by curvature is due to the induced peak This can result in significant loss of optical power transmitted to the receiver mounted on the vehicle.

As a result, when the vehicle moves, the fiber cable is unwound and unfed. By straightening the fiber, the signal attenuation rate is reduced and the signal is transmitted to the receiver. The transmitted power increases accordingly. This allows the receiver to have a sufficiently wide die. Requires Namitsu range or appropriate automatic gain control circuit (AGC) .

For example, U, S patent, patent number 4,481.542 inventor Nidomas Thovlin and others (Thos+as D, 5hovlin et al. ) Publication date: March 24, 1987. A monopulse receiver has been disclosed. This system The system employs two channels, each with a selected dynamic To provide a composite system with a desired dynamic range.

Contains circuitry to select the appropriate channel depending on the input signal amplitude .

Unfortunately, the receiver's overall dynamic range is limited by the dynamic range of each channel. Basically limited by range addition. That is, for example, by changing the length of the optical fiber. , that is, a shift in the dynamic range due to changes in the range of the system. If so, such a system configuration is not appropriate.

Therefore, a receiver connected to a coiled or folded optical fiber data link Adjusts the intensity of light incident on the fiber optic guidance system. control system is needed in this field.

Summary of the invention The present invention provides signal strength control in fiber optic communication systems. This issue Light supplies transmitters, receivers, and optical fibers between them, as well as fibers. Suitable for systems including bobbin means. This invention transmits data from a transmitter to a receiver. means for detecting the strength of the signal that is detected, and a means for detecting the strength of the signal that changes in response to the detected signal strength level; and means for generating a control signal.

Also included is means for generating a control signal to the intensity control means. Strength control means , when it is necessary to respond to a control signal and adapt to the dynamic range of the receiver, Vary the output strength of the transmitter.

Brief description of the drawing FIG. 1 is a block diagram of a general optical fiber communication system.

FIG. 2 is a block diagram showing a preferred embodiment of the signal strength control system of the present invention.

FIG. 3 shows a circuit included in the strength detection electronic circuit of the signal strength control system of the present invention. show.

FIG. 4 is a block diagram showing a transmitter of the signal strength control system of the present invention.

Detailed description of the invention As shown in FIG. 1, a typical electro-optic system 10 includes a vehicle subsystem. system 12, control station subsystem 14, and optical fiber between them. 16.

The bobbin 18 is connected to one end of the fiber optic cable 16 to provide an optical fiber connection or electrical connection. Electromechanical coupler 20 The bobbin 18 is connected to the vehicle 12 by. Electromechanical Kabra 20 is Bobi This allows the rotation of the bobbin 18 and at the same time the rotation of the bobbin 18 and the photoelectric converter. optical transducer) 22. light fu The eyebar cable 16 is connected to the control station via the control station optical multiplexer 24. It is connected to station 14. The optical multiplexers 22 and 24 are arranged in the first direction. A first known frequency optical energy and a second known frequency optical energy in a second direction are connected to an optical fiber. to the fiber cable 16.

Vehicle subsystem 12 includes a transmitter 26 and a receiver 40. Transmission section 26 receives input from multiplex data bus 30 and outputs electrical signals to transmit driver 32 A multiplexer 28 is included. The information transmitted by the data bus 30 includes, for example For example, output signals from vehicle sensors or status information from other electronic circuits. Therefore, it is configured. As is generally known, the multiplexer 28 interleave the input from the transmitter driver A composite electrical signal is generated in response to the input of the driver 32. The transmission driver 32 is a transmitter The circuit for biasing the injection laser diode or emission diode (LED) in 34 multiplexer 28, and circuitry for relaying the composite signal from multiplexer 28. These adjustments The resulting composite signals are transmitted to a transmitter 34, where they are amplified and result in an optical converted into energy.

The receiving section 40 includes a demultiplexer 42, a receiver 44, and AGC associated therewith. Includes circuit 46. Receiver 44 receives the optical signal from optical multiplexer 22 . Generally, the photodiode in receiver 44 is an electrical Generate a signal. The AGC circuit 46 controls fluctuations in the electrical signal strength within the receiver 44 to a predetermined value. If it is within the dynamic range, compensate for the variation. as commonly known In addition, signals with a magnitude exceeding the dynamic range of the AGC circuit 46 are sent to the receiver 44. saturate. At the same time, a low level signal below the dynamic range of the AGC circuit 46 is not detected by receiver 44. Therefore, the AGC circuit alone has limited It has no effect on signals exceeding the dynamic range.

Receiver 44 may include a demodulator or frequency converter, and demultiplexer 42 Process the signal before it is transmitted to the The demultiplexer 42 Performs the inverse conversion function of plexer 28. That is, the demultiplexer 42 receives the composite signal. and separates the signal into its basic components. These component signals are data It is distributed to each channel on bus 50.

Control station 14 includes a receiver 60 and a transmitter 70.

The receiving section 60 includes a receiver 64 having a demultiplexer 62 and an AGC circuit 66. include. Receiver 64 receives the optical signal from optical multiplexer 24 . receiver 64 generates an electrical signal with an amplitude proportional to the optical intensity of the received signal. The AGC circuit 66 , if the signal variation is within a predetermined dynamic range, the electrical signal in the receiver 64 Compensate for level fluctuations. As mentioned above, the AGC circuit within the control station 14 Signals exceeding the dynamic range of path 66 are similar to the operation in vehicle 12. cause difficulties. In other words, signals exceeding the dynamic range of the AGC circuit 66 are not received. signal 64, while signals of insufficient strength will not be detected. Therefore, AGC times Path 66 can only compensate for a predetermined, pre-limited range of signals.

Receiver 64 may also include demodulation or frequency conversion circuitry, including a demultiplexer. The signal is processed before being transmitted to 62. The transmitter 70 is a control station. including a multichannel multiplexer 72, which multiplexer 72 is connected to a multichannel device 90. into an electrical signal that is distributed to the control station transmit driver 74. Join. The transmit driver 74 connects the injection laser da- ter within the control station transmitter 76. A circuit that biases the diode or light emitting diode (LED) is provided.

Control station transmitter 76 converts this composite electrical signal into an optical signal; The data is transmitted to the academic multiplexer 24. The optical signal is transmitted via the fiber optic cable 16. , is transmitted to vehicle 12.

The system 100 of the present invention shown in FIG. 2 differs from the conventional system of FIG. Limitations regarding strength dynamic range can be substantially overcome. system 100 includes a vehicle subsystem 120, a control station 140, and the components therebetween. includes an optical fiber link 160. The bobbin 180 is for the optical fiber cable 160. The bobbin 180 is connected to one end and the bobbin 180 is connected to a fiber optic connection or an electromechanical coupler 20. 0 to vehicle subsystem 120. Here again, the electromechanical The bra 200 allows the bobbin 180 to rotate, and at the same time connects the bobbin 180 with the optical multiplexer. Allowing optical energy to pass between the lexers 220. Fiber optic cable 1 60 connects control station 1 via control station optical multiplexer 240. 40. Optical multiplexers 220 and 240 have optical multiplexers in first and second directions. 1 and a second frequency to the fiber optic cable 160, respectively. Ru.

A transmitter 260 and a receiver 400 are arranged in the vehicle subsystem 120.

The receiving section 400 includes a receiver 44 having a demultiplexer 420 and an AGC circuit 460. 0 and a detection circuit 480. Is the receiver 440 the optical multiplexer 220? receive optical signals from A photodetector within receiver 440 is sensitive to the intensity of the incident optical signal. Generates an electrical signal of proportional amplitude. The photodetector generated at the output 410 of the receiver 440 The detector signal is sent to demultiplexer 420 and intensity detection circuit 480 It is sampled by As shown in Figure 3, intensity detection The circuit generates a DC signal proportional to the amplitude of the electrical signal output by receiver 440. Including a low pass filter (low pass filter) 485 that is generated. nothing. The analog-to-digital (A/D) converter 490 is a low-pass filter 485 generates a digital intensity control signal at its output 540 in response to a DC signal from the . Therefore, intensity detection electronics 480 detects the intensity of the optical signal incident on receiver 440. A proportional digital intensity control signal is generated at its output 540.

Referring again to FIG. 2, the control signal from intensity sensing electronics 480 is multiplexed. bus 280 where the signal is interfaced with other signals from data bus 300. The composite electrical signal from multiplexer 280 on line 290 is the signal is transmitted to the driver electronics 320.

The electrical signal on line 290 from multiplexer 280 is shown in FIG. The information contained in the signal modulates the LED 346 via the modulation network 330. The optical signal 350 is thereby converted into an optical signal 350. As is well known in this field , the design of the modulation network 330 depends on the modulation method employed.

Optical signal 350 is routed through optical multiplexer 220 and optical fiber link 160. , to the control station subsystem 140. The link 160 is A means for providing control signals to the control station receiver 760 is provided. explained next The intensity of the optical energy received by vehicle subsystem 120 such that information about the control station subsystem is included in the optical signal 350, and that information system 140 to adjust the optical output intensity from control station transmitter 760. used to make a clause.

The output signal of receiver 640 on line 610 in FIG. 480 and incident on receiver 440 within the vehicle subsystem. Provide intensity control information corresponding to the intensity. This information is transmitted through the composite signal on line 610. is formed into separate digital intensity control signals in demultiplexer 620 and 920 to the transmit driver electronics 740.

As shown in FIG. 4, transmit driver 740 has bias network 742. includes, biases transmitter 760, and also biases line 9 from demultiplexer 620. From the digital intensity control signal on 20, a continuous time control signal is generated. this signal is used by bias network 742 to generate a bias control current . The bias control current is adjusted by adjusting the bias point of the LED 756. , adjusts the advance cuff 70 originating from the transmitter 760. Therefore, this invention means for detecting the signal strength distributed to the signal receiver 640 and responsive to the detection result; generates a control signal that responds to the

A transmitting section 700 and a receiving section 600 are arranged in the control station subsystem 140. be done. The receiving section 600 includes a demultiplexer 620 and an AGC circuit 660. The transmitter 6401 includes an intensity detection electronic circuit 680. The receiver 640 is an optical multiplexer. The optical signal is received from the comb 240. A photodetector in receiver 640 An electrical signal is generated at the receiver output 610 with an amplitude proportional to the optical signal strength. electricity Signal 610 is transmitted to demultiplexer 620 and output by intensity detection electronics 680. is sampled. As shown in FIG. 3, intensity detection electronics 680 generates a DC signal proportional to the amplitude of the electrical signal being generated at the output of the signal generator 610; It includes a low pass filter 685. The analog-to-digital converter 690 is a low-pass Digital intensity control on line 940 in response to the DC signal from filter 685 Generate a signal. Therefore, intensity detection electronics 680 is incident on receiver 640. A digital intensity control signal is generated on line 940 that is proportional to the optical signal intensity.

According to FIG. 2, the control signal on line 940 is transmitted to multiplexer 720. , where it is interleaved with other signals from data bus 90 and multiplexed. forming a composite electrical signal generated at the output cuff 30 and transmitted to the transmitter driver 740. It will be done. As shown in FIG. 4, the voltage generated at the output cuff 30 of the multiplexer is The information contained in the signal is transmitted to the photodiode 76 by the modulation network 742. 5 is converted into an optical signal 770 through modulation of a bias current. General in this field This circuit type included in modulation network 742 is well known in determined by the modulation method used.

This optical signal 770 is transmitted via optical multiplexer 240 and optical fiber link 160. and is transmitted to vehicle subsystem 120. control station subsystem included in optical signal 770 regarding the intensity of optical energy received by system 140. information is extracted within vehicle subsystem 120 and sent to vehicle transmitter 340. used to adjust the intensity of the light output generated by the

The receiver output signal 410 of FIG. In response to the optical signal strength incident on the receiver 640, the intensity detection electronics 680 Contains generated intensity control information. This signal is transmitted to the receiver in demultiplexer 420. From the composite signal appearing at output 410, a separate digital intensity control is generated on line 560. control signals and distributed to transmit driver electronics 320. As shown in Figure 4 As shown, transmit driver electronics 320 provides digital intensity control on line 560. It is equipped with a digital-to-analog converter 325 that generates a control signal from the information. Rather, it includes a bias network 330 that biases the transmitter 340.

The control signal is used by bias network 330 to generate a bias control voltage. Generate flow. This current can be adjusted by adjusting the bias point of LED 346. , adjusts the light output intensity 350 from the transmitter 340. Therefore, this invention means for detecting the signal strength distributed to the station receiver 640; A means is provided for generating a control signal in response. The invention further provides that the control signal is A means for supplying a vehicle transmitter 340 is included.

Initially, vehicle 120 is very close to control station 140 and the optical The fiber cable 160 is wound around a bobbin 180. Vehicle 120 is in control When removed from the section 140, the fiber optic cable 160 is unwound from the bobbin. Served. As is well known, curved or coiled fiber optic cable is , generally increases the attenuation of the light energy as it travels inside. That is, be As the cable is unwound from the cable 120, it is wound around the bobbin 180. The remaining cables are reduced and the optical signal loss is reduced through the fiber optic cable 160. Do a little. When vehicle 120 moves further away from control station 140 , since signal loss through the fiber optic cable 160 is reduced, the intensity sensing electronic circuit is The optical signal strength detected by paths 480 and 680 increases during this operation.

These strength detection circuits then control the signal to indicate an increase in the strength of the received signal. Signals are generated on lines 540 and 940.

The selective circuit of this invention is an automatic gain control well known in the art. The delay time caused by the propagation delay of control data through system 100 Used to compensate for signal strength fluctuations. For example, the intensity detection electronics 480 and control station transmitter driver electronics 740. A finite amount of time elapses between the reception of the relevant control data. For example, fiber optic If the incremental signal loss over data link 160 is reduced during this time , the input optical signal strength to vehicle receiver 440 is higher than the desired value. Ru. AGC circuit 460 associated with vehicle receiver 440 is in control during this time. until the output of the station transmitter 760 is adjusted by the control signal. Attenuates the optical signal.

The control signal is sent whenever the data channel updates its rate. Updated. Therefore, the advantage of this invention over the prior art is that feedback control As a result of the mechanism, the required dynamic range for AGC circuits 460 and 660 is It is possible to reduce the amount of damage.

In accordance with the present invention, to accommodate changes in the length of fiber optic data link 160; outside the operating points of control station transmitter 76o1 and vehicle transmitter 340. Adjustments are possible.

Although this invention has been described with respect to only specific embodiments, the scope of this invention extends beyond this embodiment. The examples are not limited. The description of this invention will help those skilled in the art understand the scope of this invention. Obviously, other modifications can be made that do not exceed the limits. For example, light energy The electronic circuit used to detect the incident intensity and provide a control signal indicating the incident intensity is shown here. It is not limited to the circuit described in .

Furthermore, the invention is limited to communication paths constituted by fiber optic cables. Never. Use of other suitable signal transmission media without exceeding the scope of this invention can do.

The appended claims encompass all such modifications.

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Claims (16)

[Claims] (1) A first transmitter, a first receiver, and a light linking the first transmitter and the first receiver. An optical fiber communication system comprising a fiber and bobbin means for supplying said optical fiber. the signal strength of the signal transmitted from the first transmitter to the first receiver; and means for generating a control signal that varies in response to said detected signal strength. and, intensity control means for varying the output of the first transmitter in response to the control signal; and means for supplying the control signal to the intensity control means. signal strength control system. (2) The means for supplying the control signal includes the optical fiber. The signal strength control system according to claim 1. (3) The means for supplying the control signal includes an intensity detection voltage connected to the first receiver. The signal strength control system according to claim 1, further comprising a slave circuit. (4) The means for supplying the control signal is connected to the output of the intensity detection circuit and further comprising a second transmitter for supplying the output signal to the recording optical fiber. 4. The signal strength control system according to claim 3. (5) The means for supplying the control signal is connected to the optical fiber and the means for supplying the output signal is connected to the optical fiber. 5. The signal strength of claim 4, further comprising a second receiver for receiving the signal. control system. (6) The means for supplying the control signal is arranged between the second receiver and the intensity control means. a demultiplexer connected to the second receiver and extracting the control signal from the output of the second receiver; 6. The signal strength control system according to claim 5, further comprising support means. (7) The detection means further comprises intensity detection electronics responsive to the detection signal. The signal strength control system according to claim 1, characterized in that: (8) The detection means generates a detection signal having an amplitude proportional to the signal strength. 8. The signal strength control according to claim 7, further comprising a photodetector. system. (9) The intensity detection electronic circuit is configured to receive a DC signal having a magnitude proportional to the amplitude of the detection signal. 9. The signal strength generator according to claim 8, further comprising a low-pass filter that generates a signal. degree control system. (10) The intensity detection electronic circuit is connected to the output of the low-pass filter. Signal strength according to claim 9, further comprising an analog-to-digital converter. control system. (11) The intensity control means is a transmission driver electronic circuit connected to the first transmitter. 2. The signal strength control system according to claim 1, further comprising a signal strength control system. (12) The transmit driver electronics include a digital analyzer that forms the intensity control signal. 12. The signal strength control system of claim 11, further comprising a log converter. (13) The transmitter electronics is configured to control a bias control voltage in response to the intensity control signal. 13. The method of claim 12, further comprising a bias network for generating a flow. Built-in signal strength control system. (14) The bias control current is supplied to an optical signal source within the first transmitter. The signal strength control system according to claim 13, characterized in that: (15) A first transmitter, a first receiver, and an optical fiber connecting the first transmitter and the first receiver. Optical fiber communication system comprising a fiber and bobbin means for supplying said fiber , the signal strength is compared to the signal strength of the signal received from the first transmitter to the first receiver. a photodetector disposed within the first receiver for generating a detection signal having a representative amplitude; a detector, generating a DC signal having a magnitude proportional to the amplitude of the detection signal; a low-pass filter connected to the first receiver; and a digital filter in response to the DC signal. an analog-to-digital converter connected to said first receiver; exchanger and injecting said composite digital intensity control signal into an optical carrier generated within a second transmitter; generates a light intensity control signal and connects it to the analog-to-digital converter. a modulation network connected to a first light source that provides the light control signal to the optical fiber and is coupled to the second transmitter; a multiplexer, converting the optical control signal from the optical fiber into the optical control signal; a second optical multiplexer decoupled to a second receiver responsive to generate an electrical control signal; and, Recovering the digital intensity control signal from the electrical control signal and receiving the DS AI2 a demultiplexer connected to the analyzer and an analyzer in response to said digital intensity control signal; A digital analyzer that provides the log strength control signal and is connected to the demultiplexer. log converter, generating a bias control current in response to the analog intensity control signal; - Bias network connected to analog converter. a light source responsive to the bias control current and disposed within the first transmitter; (16) a transmitter, a receiver, an optical fiber connecting the transmitter and the receiver; In an optical fiber communication system having a bobbin means for supplying the fiber, a ) detecting the signal strength provided from the transmitter to the receiver; b) generating a control signal that varies in response to the detected signal strength; , c) changing the signal extremity from the transmitter in response to the control signal; and adjusting the signal strength of the signal incident on the receiver. Method.