CN112165359A - Optical transmission system with receiving and transmitting multipath signals - Google Patents
Optical transmission system with receiving and transmitting multipath signals Download PDFInfo
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- CN112165359A CN112165359A CN202011041814.1A CN202011041814A CN112165359A CN 112165359 A CN112165359 A CN 112165359A CN 202011041814 A CN202011041814 A CN 202011041814A CN 112165359 A CN112165359 A CN 112165359A
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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
- H04B10/2575—Radio-over-fibre, e.g. radio frequency signal modulated onto an optical carrier
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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
- H04B10/2575—Radio-over-fibre, e.g. radio frequency signal modulated onto an optical carrier
- H04B10/25752—Optical arrangements for wireless networks
- H04B10/25758—Optical arrangements for wireless networks between a central unit and a single remote unit by means of an optical fibre
- H04B10/25759—Details of the reception of RF signal or the optical conversion before the optical fibre
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Abstract
The invention provides an optical transmission system with receiving and transmitting multi-path signals; the system comprises a shore end signal monitoring system and a ship end signal monitoring system, wherein the shore end signal monitoring system and the ship end signal monitoring system are controlled by a function control system, and the shore end signal monitoring system is accessed to a local contact signal and a multipath transmission signal; the optical transmission of four paths of analog signals and one path of single-source contact signals can be realized simultaneously without mutual interference, and the optical fiber cable has the functions of carrier signal identification, signal intensity detection and loop self-checking.
Description
Technical Field
The present invention relates to an optical transmission system having a function of transmitting and receiving a plurality of signals.
Background
The ship-shore connection system comprises a cable connection mode, an optical fiber connection mode and the like, one of key core technologies in the ship-shore connection system specially designed for the liquefied natural gas ship in the optical fiber connection mode, and the optical transmission system modem relates to multiple frequency carriers, easily generates multiple harmonic waves and needs to improve the stray suppression capability of the module.
Disclosure of Invention
To solve the above technical problem, the present invention provides an optical transmission system with transceiving multiple signals.
The invention is realized by the following technical scheme.
The invention provides an optical transmission system with receiving and transmitting multi-path signals; the system comprises a shore end signal monitoring system and a ship end signal monitoring system, wherein the shore end signal monitoring system and the ship end signal monitoring system are controlled by a function control system, and the shore end signal monitoring system is accessed to a local contact signal and a multipath transmission signal;
the shore end signal monitoring system and the ship end signal monitoring system both comprise a four-path signal modem to perform double-sideband frequency division multiplexing processing on the multi-path transmission signals.
The multi-path transmission signals comprise four paths of communication signals and one path of local contact signals;
the shore end signal monitoring system converts, modulates and digitally up-converts the four communication signals and inputs the signals into the ship end signal monitoring system;
the shore end signal monitoring system modulates and converts the local contact signals and inputs the signals into the ship end signal monitoring system.
The shore end signal monitoring system further comprises driving isolators which are arranged at two ends of the local contact signal processing.
The ship-end signal monitoring system sequentially carries out digital down-conversion, amplification, conversion, carrier identification, demodulation and conversion on the received four communication signals and then transmits the four communication signals to a ship end.
The ship-end signal monitoring system amplifies, detects, converts and frequency detects the received local contact signals to form a far-end contact signal and a telephone ring calling signal respectively.
The ship-end signal monitoring system respectively outputs a far-end contact signal and a telephone ring calling signal through two isolation drivers.
And the local signal is modulated by FSK modulation to carry out single-contact signal modulation.
The four-path signal modem adopts amplitude modulation, and the demodulator adopts an envelope detection mode.
The four communication signals comprise monitoring data, a hotline telephone, a public telephone and an internal telephone.
The conversion is AD/DA conversion.
The invention has the beneficial effects that: by employing a multiplexer to receive analog signals from multiple sources, each with its own independent bandwidth, and then combining these signals into another, larger bandwidth, more complex signal, the resulting signal is transmitted over some medium to a destination. The available bandwidth of the transmission medium is divided into a plurality of separate ranges or channels, a carrier signal is defined for each channel, and corresponding guard bands are set up between the channels for isolation in order to prevent mutual interference between adjacent channels. The channels are themselves separated by guard bands to prevent interference between adjacent channels, and the resulting signals are transmitted and received by another multiplexer. The received signal is separated from each independent modulation signal by a band-pass filter, and finally, the original signal is recovered by demodulation.
Drawings
FIG. 1 is a schematic structural view of the present invention;
FIG. 2 is a schematic diagram of the optical transmission system of the present invention;
fig. 3 is a schematic diagram of the operation of the modem of the optical transmission system of the present invention;
FIG. 4 is a schematic diagram of the control timing sequence of the interface communication module of the optical transmission system according to the present invention;
Detailed Description
The technical solution of the present invention is further described below, but the scope of the claimed invention is not limited to the described.
An optical transmission system with functions of receiving and transmitting multi-path signals comprises a modem of four-path signals, a modem of single-source contact signals, a frequency detection module, an interface communication module, a loop detection module, a carrier identification module, a signal up-down frequency conversion module, a digital-to-analog conversion module and an analog-to-digital conversion module. And 4 optical fiber interfaces and a plurality of analog signal transceiving and control signal interaction interfaces are arranged externally.
The modem of the four-path signal, the modem of the contact signal, the frequency detection module, the interface communication module, the loop detection module and the carrier identification module are integrated in the FPGA chip for full digitalization. The analog-digital conversion module is realized by adopting a multi-channel serial ADC chip, and the digital-analog conversion module is also realized by adopting a multi-channel serial DAC chip.
The four-path signal modem mainly completes the functions of double-sideband frequency division multiplexing modulation and demodulation of the ship-shore two-end monitoring system signal MON and the three-path telephone voice signal; the modem of the single-source contact signal CON mainly completes the FSK modulation and demodulation function of the contact signal; the frequency detection module mainly completes the functions of detecting the frequency of the contact modulation signal and detecting the frequency of the telephone call; the interface communication module mainly completes the SPI serial communication function of signals between the function control system and the interface communication module; the loop detection module mainly completes the detection functions of self-modulation and self-demodulation of the ship shore end and is used for detecting whether the module works normally; the carrier identification module mainly completes the function of carrier identification of receiving appointed modulation signals at two ends of a ship bank; the signal up-down conversion module mainly realizes the functions of performing up-conversion on four paths of mixed modulation signals at a modulation end to generate intermediate frequency signals with carrier frequency of 64MHz, transmitting the intermediate frequency signals through optical fibers, receiving the optical fiber transmission at a demodulation end, and then removing the carrier frequency of 64MHz through down-conversion; the analog-to-digital conversion module and the digital-to-analog conversion module realize the conversion function of digital and analog signals by controlling the multi-channel ADC and DAC chips.
The two modems are connected with the frequency detection module, the interface communication module, the loop detection module, the carrier identification module, the signal up-down frequency conversion module, the analog-to-digital conversion module and the digital-to-analog conversion module through power supplies and control signals.
The analog-to-digital conversion module and the digital-to-analog conversion module are connected with an isolation driver and a signal conditioning circuit, the modem, the frequency detection module, the loop detection module and the carrier identification module are realized in a full digitalization mode on FPGA software, and the modulation adopts a direct digital synthesis DDS technology to generate carriers with corresponding frequencies.
The modem of the four-path signal adopts a double-sideband frequency division multiplexing technology. The four-way signals are mainly supervisory signals, hotline telephone signals, public telephone signals and internal telephone signals. The modulated carrier is divided into a ship shore end, four paths of signals at the shore end are respectively modulated to carrier frequency bands with the frequencies of 18kHz, 30kHz, 42kHz and 54kHz, and four paths of signals at the ship end are respectively modulated to carrier frequency bands with the frequencies of 78kHz, 90kHz, 102kHz and 114 kHz. Monitoring signals are transmitted to the function control system by the shore end monitoring system through the standard RS232 serial interface to be FSK modulated, then are input to the optical transmission module to be modulated and demodulated by double-sideband frequency division multiplexing, and the demodulated monitoring analog signals are transmitted to the ship end monitoring system through the standard RS232 serial interface after being FSK demodulated by the function control system. The shore end is responsible for modulating and sending monitoring signals, and the ship end is responsible for demodulating and receiving the monitoring signals. The hotline telephone adopts a carrier frequency offset mode to achieve the calling function, the transmission of normal voice adopts a double-sideband frequency division multiplexing technology, and the frequency of a transmission voice signal is controlled within the range of 300Hz to 3400 Hz. The public telephone and the internal telephone adopt a direct calling mode, namely, the telephone is taken up to orally call and the opposite side is reminded by using a loudspeaker to be placed outside, the transmission of normal voice adopts a double-sideband frequency division multiplexing technology, and the frequency of a transmission voice signal is controlled within the range of 300 Hz-3400 Hz.
The contact signal modem employs FSK modulation techniques. The high level of the contact signal indicates a fail-safe mode and the low level indicates a safe mode. The fail-safe mode modulated carrier is 10kHz and the safe mode modulated carrier is 5 kHz. The contact signal demodulation end of the optical transmission system only receives the signals of the two frequencies, and the signals of other frequencies are considered as abnormal signals.
The four-channel signal modem comprises the normal transmission of telephone voice and the transmission of telephone ring, wherein each channel of signal adopts amplitude modulation in normal modulation, and the demodulator adopts an envelope detection mode. The band-pass filter designed in the modem adopts a kaiser window function FIR digital filter. The hotline telephone ring call uses a frequency offset of 2.6kHz to achieve the purpose of distinguishing the voice signal from the ring call signal. The public telephone and the internal telephone adopt a direct calling mode, namely, the public telephone and the internal telephone remind the opposite party by taking up the telephone to call orally and using a loudspeaker to put the telephone out.
The frequency detection module mainly completes the functions of detecting the frequency of the contact modulation signal and detecting the frequency of the telephone call. Since the contact signal demodulating portion receives signals of only two frequencies, frequency detection of the contact modulated signal is required. For the calling signal of telephone, the calling of hotline telephone generates calling control signal according to frequency deviation 2.6kHz, then uses a narrow-band digital band-pass filter to identify the signal of the frequency, when the value of the signal reaches a certain threshold value, the optical transmission module generates ringing signal to control the ringing of telephone
The carrier recognition module is designed to receive only carrier signals with specific frequency, the monitoring signals, the three paths of voice signals and the contact signals are modulated to corresponding frequencies, and after the mixed modulation signals at the demodulation end are received by the optical fibers, the four paths of signals are separated through four narrow-band digital band-pass filters. The separated signals are divided into four paths according to corresponding carrier frequencies, and whether the frequency of the carrier signals is correct or not is judged by setting the level value threshold of the carrier signals so as to realize the identification of the carrier.
The loop detection module mainly completes the functions of self-modulation and self-demodulation of the ship shore end, is connected with the control signal, sets band-pass filters under different frequencies according to the requirements of the control instruction, allows the modulation and demodulation of the modulation signal with specific frequency, and transmits the result to the function control system through SPI serial port communication.
The interface communication mainly completes the serial port communication between the optical transmission module and the function control module. The communication interface of the function control system and the optical transmission system adopts a three-wire system SPI communication interface, and the communication transmission baud rate of the SPI serial port is 1 Mbps. The optical transmission system is controlled by the instruction of the function control system to switch different functions. The signal up-down conversion module mainly realizes the functions of performing up-conversion on four paths of mixed modulation signals at a modulation end to generate intermediate frequency signals with carrier frequency of 64MHz, transmitting the intermediate frequency signals through optical fibers, receiving the optical fiber transmission at a demodulation end, and then removing the carrier frequency of 64MHz through down-conversion; the analog-to-digital conversion module and the digital-to-analog conversion module realize the conversion function of digital and analog signals by controlling the multi-channel ADC and DAC chips.
The modem can distinguish the ship shore end according to the instruction of the function control system. The system is simultaneously installed on a ship-end cabinet and a bank-end cabinet, the two systems are connected by adopting optical fibers, and the optical fiber connection adopts multimode optical fibers and a double-line full-duplex mode. The 3-path telephone and the 1-path monitoring data adopt a 2-path optical fiber one-transmitting-one-receiving full duplex circuit; the contact signal adopts a 2-path optical fiber one-sending-one-receiving full duplex circuit.
And the analog-to-digital conversion module is used for conditioning the analog signal before the analog signal is input into the ADC for analog-to-digital conversion, controlling the voltage of the input signal to be between 0V and 5V and ensuring that the phenomenon of overmodulation of the modulated signal and the phenomenon of distortion of the demodulated signal cannot occur.
The carrier frequency synthesis technology adopts DDS (direct digital synthesis) technology, and can generate carrier signals with different frequencies according to the frequency control words.
The method adopts a full-digital implementation mode, has high circuit integration level, simple circuit and easy debugging, adopts software to realize modulation, and is convenient to modify according to the interface characteristics in the butt joint process.
The optical transmission system and the function control system are communicated through an interface, and the optical transmission system can switch ship-shore end instructions at any time according to the control instructions of the function control system, so that the module can be used universally at the ship end and the shore end. And the functions of loop detection, work and non-work modes and the like can be executed according to the control instruction.
The digital filter is designed by adopting a kaiser window function, the amplitude-frequency characteristic of the kaiser window in the passband range is flat and straight, the attenuation is low, the size of a side lobe of the window function can be controlled by changing the shape of the window function, and the shape of the window function can be determined according to the attenuation index of the filter in the design.
The structure of the system is shown in fig. 1, and the system comprises a modem of four paths of signals, a modem of a single source contact signal (CON), a frequency detection module, an interface communication module, a loop detection module, a carrier identification module, a signal up-down frequency conversion module, a digital-to-analog conversion module and an analog-to-digital conversion module.
The four-path signal modem, the single-source contact signal modem, the frequency detection module, the interface communication module, the loop detection module and the carrier identification module are integrated in an FPGA chip and are realized in a full digitalization mode.
The signal conditioning circuit mainly controls the frequency range and the voltage value range of the input and output signals.
The isolation driving circuit is mainly used for increasing the safety of the module circuit.
The carrier circuit and the signal driving circuit mainly realize signal up-conversion, and the transmitting end utilizes the carrier circuit to generate 64MHz high-frequency carrier to up-convert the modulation signal.
The detection circuit mainly removes 64MHz high frequency from four paths of mixed modulation signals to realize down conversion function and envelope detection of contact modulation signals.
The AD circuit mainly realizes the analog-to-digital conversion function.
The DAC circuit mainly realizes the digital-to-analog conversion function.
The transmission of the I/O signal mainly realizes the interface communication function with the function control module.
The signal amplification circuit mainly realizes the control function of the input analog signal voltage.
The contact signal light emission (receiving) and the AUDIO light emission (receiving) adopt multimode optical fibers with the wavelength of 850nm and a double-wire full-duplex mode. The 3-path telephone and 1-path monitoring system signal adopts a 2-path optical fiber one-transmitting-one-receiving full duplex circuit; the contact signal adopts a 2-path optical fiber one-sending-one-receiving full duplex circuit.
The FPGA full digitalization realizes that a modem of four paths of signals, a modem of single-source contact signals, a frequency detection module, an interface communication module, a loop detection module and a carrier recognition module are connected by control signals.
The working principle of the optical transmission system is as follows:
as shown in fig. 1, the function control system provides a control signal, and transmits the control signal to the FPGA chip of the optical transmission system through the signal socket of the optical fiber connection board, and controls the modulation and demodulation of the four signals, the modulation and demodulation of the single-source contact signal, the frequency detection, the interface communication, the loop detection, and the carrier identification by using the interface communication, and each module starts to work. A communication timing diagram of the function control system and the optical transmission system interface is shown in fig. 3.
As shown in fig. 2, the four-channel signal modem uses a double-sideband frequency division multiplexing method, and uses a DDS frequency control word to generate carriers with different frequencies for signal modulation. The Low Pass Filter (LPF) and the Band Pass Filter (BPF) in the algorithm both adopt kaiser window functions to design filters with different pass bands so as to distinguish all paths of signals and reduce mutual interference among all paths of signals.
In summary, the present invention employs the double-sideband frequency division multiplexing modulation and demodulation technology to realize the transmission of multiple signals and employs the FSK modulation and demodulation method to realize the transmission of contact signals. And a digital integration implementation mode is adopted, so that the circuit is simple and easy to debug.
Claims (10)
1. An optical transmission system having a function of transmitting and receiving a plurality of signals, comprising: the system comprises a shore end signal monitoring system and a ship end signal monitoring system, wherein the shore end signal monitoring system and the ship end signal monitoring system are controlled by a function control system, and the shore end signal monitoring system is accessed to a local contact signal and a multipath transmission signal;
the shore end signal monitoring system and the ship end signal monitoring system both comprise a four-path signal modem to perform double-sideband frequency division multiplexing processing on the multi-path transmission signals.
2. The optical transmission system having a function of transmitting and receiving a multiplex signal according to claim 1, wherein: the multi-path transmission signals comprise four paths of communication signals and one path of local contact signals;
the shore end signal monitoring system converts, modulates and digitally up-converts the four communication signals and inputs the signals into the ship end signal monitoring system;
the shore end signal monitoring system modulates and converts the local contact signals and inputs the signals into the ship end signal monitoring system.
3. The optical transmission system having a function of transmitting and receiving a multiplex signal according to claim 2, wherein: the shore end signal monitoring system further comprises driving isolators which are arranged at two ends of the local contact signal processing.
4. The optical transmission system having a function of transmitting and receiving a multiplex signal according to claim 1, wherein: the ship-end signal monitoring system sequentially carries out digital down-conversion, amplification, conversion, carrier identification, demodulation and conversion on the received four communication signals and then transmits the four communication signals to a ship end.
5. The optical transmission system having a function of transmitting and receiving a multiplex signal according to claim 1, wherein: the ship-end signal monitoring system amplifies, detects, converts and frequency detects the received local contact signals to form a far-end contact signal and a telephone ring calling signal respectively.
6. The optical transmission system having a function of transmitting and receiving a multiplex signal according to claim 5, wherein: the ship-end signal monitoring system respectively outputs a far-end contact signal and a telephone ring calling signal through two isolation drivers.
7. The optical transmission system having a function of transmitting and receiving a multiplex signal according to claim 2, wherein: and the local signal is modulated by FSK modulation to carry out single-contact signal modulation.
8. The optical transmission system having a function of transmitting and receiving a multiplex signal according to claim 1, wherein: the four-path signal modem adopts amplitude modulation, and the demodulator adopts an envelope detection mode.
9. The optical transmission system having a function of transmitting and receiving a multiplex signal according to claim 2, wherein: the four communication signals comprise monitoring data, a hotline telephone, a public telephone and an internal telephone.
10. The optical transmission system having functions of transmitting and receiving multiplex signals according to any one of claims 2, 4 and 5, wherein: the conversion is AD/DA conversion.
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| CN202011041814.1A CN112165359A (en) | 2020-09-28 | 2020-09-28 | Optical transmission system with receiving and transmitting multipath signals |
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Application publication date: 20210101 |