Optical telephone solution system of automatic pairing communication mode

Abstract

The invention belongs to the field of optical fiber telephones, and discloses an optical telephone solving system in an automatic pairing communication mode, which comprises a single chip microcomputer control unit, a transmitting unit and a receiving unit, the single chip microcomputer control unit is used for generating and identifying handshake pulse signals; the working wavelengths of the transmitting and receiving channels are controlled; the output volume is adjusted by controlling the digital potentiometer; the transmitting unit is used for outputting a PWM (Pulse Width Modulation) waveform modulated by an audio signal through the audio modulation circuit and controlling the constant-current switching circuit and the laser module through the PWM waveform; and the receiving unit is used for amplifying, shaping and filtering the light current signal and inputting the light current signal into the single chip microcomputer. Telephones of two parties do not need to be distinguished according to uplink and downlink wavelengths; a digital modulation technology is used to reduce noise and enhance anti-interference performance; and short-distance communication and long-distance communication are both considered, and gain switching is not needed.

Description

Technical Field

[0001] The invention relates to the field of optical fiber telephones, and in particular to an optical telephone solution system with automatic pairing communication mode. Background Art

[0002] In the layout and maintenance of optical network infrastructure, we often encounter places or facilities such as underground pipe corridors, tunnels, and the wild where there is no cellular mobile signal or it is inconvenient to use radio, which brings obstacles to construction. In this case, we can generally use the already laid optical fiber trunk line to connect the optical fiber telephone to transmit audio to realize calls, which is convenient for the construction party to communicate and connect.

[0003] Existing fiber-optic telephone solutions use a single wavelength laser with a PIN photodiode with a fixed wavelength bandpass filter on the optical link (in Figure 1 In this paper, 1310nm and 1550nm are used as examples) and 3db coupler are used to realize wavelength division multiplexing, and full-duplex communication is realized on this basis. The optical link diagram is as follows: Figure 1 shown.

[0004] In terms of signal processing circuits, the audio voltage signal collected by the microphone is amplified, modulated and superimposed on the bias current of the laser, so that the audio signal is superimposed on the laser output power. The remote receiving part uses a PIN photodiode to convert the received laser power into photocurrent, and then uses a transimpedance amplifier to amplify the weak current signal and convert it into a voltage signal. Finally, the audio amplifier removes the DC component of the voltage signal from the transimpedance amplifier and further amplifies it to restore the original audio signal. Its schematic diagram is shown below. Figure 2-Figure 11 However, the existing solutions still have the following shortcomings:

[0005] (1) The machine is usually equipped with only a single-wavelength laser, and there is no circuit or control mechanism for distinguishing the uplink and downlink wavelengths. Therefore, it is necessary to strictly distinguish between machine A and machine B according to the uplink and downlink wavelengths. If one of them cannot be used, it is necessary to find a machine with the same uplink and downlink wavelengths to replace it, otherwise communication will not be possible. Moreover, if the personnel on both sides of the optical fiber mistakenly hold machines with the same uplink and downlink wavelengths, communication will also be impossible. This brings inconvenience to use and management.

[0006] (2) The existing solution uses analog modulation technology, where the audio signal is directly superimposed on the laser drive current, i.e. DC bias modulation. This modulation method has poor anti-interference performance and the signal-to-noise ratio decreases rapidly with the increase of optical fiber length. In actual use, the communication distance is short and the noise is high.

[0007] (3) The existing scheme uses DC bias modulation at the transmitter, which causes a large DC component in the photocurrent at the receiver, limiting the design of the signal amplification circuit and making it impossible to take into account both small and large signal conditions. In actual use, users need to manually switch the gain multiple according to the length of the communication distance. When the communication distance is between long-distance communication and short-distance communication, the high-gain mode may not work properly, and the low-gain mode may have too low volume and too much noise, which is inflexible in use.

[0008] Therefore, how to provide an optical telephone solution system with automatic pairing communication mode is a problem that needs to be solved urgently. Summary of the invention

[0009] The embodiment of the present invention provides an optical telephone solution system with an automatic pairing communication mode to solve the problems of inconvenient communication, short communication distance, high noise and inflexible use of optical fiber telephones in the prior art.

[0010] In order to have a basic understanding of some aspects of the disclosed embodiments, a brief summary is given below. This summary is not intended to be a general review, nor is it intended to identify key / important components or to delineate the scope of protection of these embodiments. Its only purpose is to present some concepts in a simple form as a preface to the detailed description that follows.

[0011] According to an embodiment of the present invention, an optical telephone solution system with automatic pairing communication mode is provided.

[0012] In one embodiment, an optical telephone solution system with automatic pairing communication mode includes: a single-chip microcomputer control unit, a transmitting unit and a receiving unit; the transmitting unit is connected to the receiving unit, and the single-chip microcomputer control unit is connected to the transmitting unit and the receiving unit; the single-chip microcomputer control unit is used to generate and identify handshake pulse signals; control the working wavelengths of the transmitting and receiving channels; adjust the output volume by controlling a digital potentiometer; the transmitting unit is used to output a PWM waveform modulated by an audio signal through an audio modulation circuit, and control a constant current switch circuit and a laser module through the PWM waveform; the receiving unit is used to amplify, shape and filter the photocurrent signal, and input the photocurrent signal into the single-chip microcomputer.

[0013] In one embodiment, the audio modulation circuit includes a preamplifier, a limiting amplifier, a triangular wave generator and a voltage comparator; outputting a PWM waveform modulated by an audio signal through the audio modulation circuit includes: amplifying a voltage signal from an audio acquisition device through a preamplifier and a limiting amplifier in turn, and limiting the fluctuation range of the voltage signal to a preset range; generating a triangular wave of a fixed frequency by using a triangular wave generator; connecting the voltage signal output by the limiting amplifier through the same-phase input terminal of the voltage comparator, connecting the triangular wave of a fixed frequency output by the triangular wave generator through the inverting input terminal of the voltage comparator, and outputting a PWM waveform modulated by the audio signal through the output terminal of the voltage comparator.

[0014] In one embodiment, the duty cycle of the PWM waveform is the same as the cycle of the triangle wave output by the triangle wave generator.

[0015] In one embodiment, the constant current switch circuit includes a laser diode LD1, a resistor R3, a transistor Q4, a resistor R1, a MOS transistor Q2, a MOS transistor Q1, a transistor Q3, a resistor R2, a resistor R4, a resistor R6, a resistor R5, a transistor Q5, a voltage reference V1, a capacitor C1, a capacitor C2, a resistor R7, a resistor R8, a resistor R9, a resistor R10, a resistor R11, a resistor R12, a resistor R13, a resistor R14, a resistor R15, a resistor R16, a diode D1, a diode D2, a transistor Q6 and a transistor Q7; wherein the fourth end of the laser diode LD1 is connected to the third end of the MOS transistor Q2, and the first end of the MOS transistor Q2 is connected in sequence The MOS transistor Q2 is connected to one end of the resistor R1 and the second end of the transistor Q4, the first end of the transistor Q4 is connected to one end of the resistor R3, the second end of the MOS transistor Q2 is connected to the other end of the resistor R1, one end of the resistor R2 and the second end of the MOS transistor Q1 in sequence, the third end of the MOS transistor Q1 is connected to the eighth end of the laser diode LD1, the other end of the resistor R2 is connected to the first end of the MOS transistor Q1 and the second end of the transistor Q3 in sequence, the first end of the transistor Q3 is connected to one end of the resistor R4; the second end and the sixth end of the laser diode LD1 are both connected to one end of the resistor R5, the other end of the resistor R5 is connected to the second end of the transistor Q5, the first end of the transistor Q5 is connected to the One end of the resistor R6 is connected to the first end of the voltage reference V1 and the second end of the voltage reference V1, the other end of the resistor R6 is connected to one end of the capacitor C1, the other end of the capacitor C1 is sequentially connected to the third end of the voltage reference V1, one end of the resistor R10 and one end of the resistor R11, the other end of the resistor R10 is sequentially connected to the third end of the transistor Q5, the first end of the resistor R7, the third end of the resistor R8, one end of the capacitor C2 and one end of the resistor R9, the second end and the third end of the resistor R7 are connected to the other end of the resistor R11, the second end and the first end of the resistor R8 are connected to one end of the resistor R12, the other end of the resistor R12 is sequentially connected to the other end of the capacitor C2, the other end of the resistor R9 The first end of the transistor Q6 and the second end of the transistor Q7 are connected to one end, the second end of the transistor Q7 and the cathode of the diode D1 and the cathode of the diode D2, the anode of the diode D1 is connected to the first end of the transistor Q6, one end of the resistor R13, one end of the capacitor C3 and one end of the resistor R15 in sequence, the other end of the resistor R13 is connected to the other end of the capacitor C3, the other end of the resistor R15 is connected to the third end of the transistor Q6, the third end of the transistor Q7 and one end of the resistor R16 in sequence, the other end of the resistor R16 is connected to the first end of the transistor Q7, the anode of the diode D2, one end of the resistor R14 and one end of the capacitor C4 in sequence, and the other end of the resistor R14 is connected to the other end of the capacitor C4.

[0016] In one embodiment, transistor Q5 and voltage reference V1 form a constant current circuit; resistor R7 and resistor R8 are used to adjust the driving current and bias current of laser diode LD1.

[0017] In one embodiment, amplifying, shaping and filtering the photocurrent signal and inputting the photocurrent signal into a single-chip microcomputer includes: a receiving unit amplifying the photocurrent signal through a limiting transimpedance amplifier and an inverting amplifier, and using the inverting amplifier to shape the photocurrent signal; filtering out the high-frequency carrier signal in the photocurrent signal through a filter, and outputting an audio signal; acquiring the photocurrent signal through a single-chip microcomputer, and using the single-chip microcomputer control unit to identify the handshake pulse signal when shaking hands.

[0018] In one embodiment, the limiting transimpedance amplifier includes an optical receiving module PIN1A, a diode D21, a resistor R21, a capacitor C21, a capacitor C22, a capacitor C23, a chip U1, a resistor R23, a capacitor C24, a resistor R22, a resistor R24, a junction field effect transistor Q11 and a junction field effect transistor Q22; wherein a first end of the diode D21 is sequentially connected to one end of the resistor R21, one end of the capacitor C21, a second end of the optical receiving module PIN1A and a third end of the junction field effect transistor Q11, and a second end of the diode D21 is sequentially connected to the other end of the resistor R21, the other end of the capacitor C21, One end of capacitor C24 is connected to the first end of chip U1, the fifth end of chip U1 is connected to one end of resistor R23, the sixth end of chip U1 is connected to one end of capacitor C23 and one end of capacitor C22 in sequence, and the other end of capacitor C23 is connected to the other end of capacitor C22; the fourth end of chip U1 is connected to one end of resistor R22 and the first end of junction field effect transistor Q22 in sequence, the other end of resistor R22 is connected to the second end of junction field effect transistor Q11, the second end of junction field effect transistor Q22 is connected to one end of resistor R24, and the other end of resistor R24 ​​is connected to the third end of junction field effect transistor Q22.

[0019] In one embodiment, the junction field effect transistor Q11, the junction field effect transistor Q22, the resistor R22, the resistor R24 ​​and the chip U1 form a composite amplifier, and the composite amplifier reduces the noise caused by the input bias current and input capacitance of the operational amplifier.

[0020] In one embodiment, the handshake process includes: the microcontrollers of the handshaking devices transmit audio carrier signals in a preset channel alternately at random periods; when the local device continuously captures several pulses of the audio carrier signal and the signal period meets the preset requirements, the handshake is successful, and the current uplink and downlink wavelengths of the local device are locked, and the other device locks the opposite uplink and downlink wavelengths.

[0021] In one embodiment, the acquisition of the random cycle includes: generating a random number within a preset range based on the random noise collected by the analog-to-digital converter in combination with a random number generation algorithm, and generating a random cycle according to the random number.

[0022] The technical solution provided by the embodiment of the present invention may have the following beneficial effects:

[0023] (1) The present invention provides an optical telephone solution system with automatic pairing communication mode, which does not need to distinguish between A and B machines according to the uplink and downlink wavelengths; uses digital modulation technology to reduce noise and enhance anti-interference. It takes into account both short-distance communication and long-distance communication without switching gain.

[0024] (2) The present invention uses a PWM waveform generated by the audio modulation part to control the constant current switch circuit and the laser module, which can accurately adjust the drive current and bias current and obtain a very high current rise / fall edge speed without high total device cost. The limiting transimpedance amplifier uses discrete JFETs and operational amplifiers to form a composite transimpedance amplifier, and adds a diode limiting circuit to improve the circuit's overload resistance, effectively solving the problem of taking into account both large and small signals under high gain conditions. Jitter is inserted during the handshake process to prevent the local and remote ends from entering the handshake process at the same time, which will cause the detection phase to be the same or similar, thereby causing the handshake process to fail or take too long.

[0025] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0027] Figure 1 This is the optical link diagram of the existing optical fiber telephone;

[0028] Figure 2 This is one of the schematic diagrams of the transmitting part of the existing fiber-optic telephone;

[0029] Figure 3 This is the second schematic diagram of the transmitting part of the existing optical fiber telephone;

[0030] Figure 4 This is the third schematic diagram of the transmitting part of the existing optical fiber telephone;

[0031] Figure 5 This is the fourth schematic diagram of the transmitting part of the existing optical fiber telephone;

[0032] Figure 6 This is one of the schematic diagrams of the receiving part of an existing optical telephone;

[0033] Figure 7 This is the second schematic diagram of the receiving part of the existing optical telephone;

[0034] Figure 8 This is the third schematic diagram of the receiving part of the existing optical telephone;

[0035] Fig. 9 This is the fourth schematic diagram of the receiving part of the existing optical telephone;

[0036] Fig.10 This is the fifth schematic diagram of the receiving part of the existing optical telephone;

[0037] Fig.11 This is the sixth schematic diagram of the receiving part of the existing optical telephone;

[0038] Fig.12 This is one of the principle block diagrams of an optical telephone solution system of an automatic pairing communication mode according to an exemplary embodiment;

[0039] Fig.13 This is a second principle block diagram of an optical telephone solution system of an automatic pairing communication method according to an exemplary embodiment;

[0040] Fig.14 is a circuit block diagram of an audio signal modulation part according to an exemplary embodiment;

[0041] Fig.15 is a schematic diagram of a constant current switch circuit according to an exemplary embodiment;

[0042] Fig.16 is a block diagram of a receiving part according to an exemplary embodiment;

[0043] Fig.17 is a partial schematic diagram of a limiting transimpedance amplifier according to an exemplary embodiment;

[0044] Fig.18 is a schematic diagram showing a handshake window being too narrow according to an exemplary embodiment;

[0045] Fig.19 The figure is a diagram of a random jitter identification periodic handshake window according to an exemplary embodiment. DETAILED DESCRIPTION

[0046] The following description and accompanying drawings fully illustrate the specific embodiments of this article so that those skilled in the art can practice them. Parts and features of some embodiments may be included in or replace parts and features of other embodiments. The scope of the embodiments of this article includes the entire scope of the claims, as well as all available equivalents of the claims. Herein, the terms "first", "second", etc. are only used to distinguish one element from another, without requiring or implying any actual relationship or order between these elements. In fact, the first element can also be called the second element, and vice versa. Moreover, the terms "include", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, so that the structure, device or equipment including a series of elements includes not only those elements, but also other elements that are not explicitly listed, or also include elements inherent to such structure, device or equipment. In the absence of more restrictions, the elements defined by the sentence "including one..." do not exclude the existence of other identical elements in the structure, device or equipment including the elements. Each embodiment is described in a progressive manner herein, and each embodiment focuses on the differences from other embodiments, and the same and similar parts between the embodiments can be referred to each other.

[0047] The terms "longitudinal", "lateral", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like used herein to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing this article and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In the description herein, unless otherwise specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a mechanical connection or an electrical connection, it can also be the internal connection of two elements, it can be a direct connection, or it can be an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0048] As used herein, the term "plurality" means two or more than two, unless otherwise specified.

[0049] In this document, the character " / " indicates that the preceding and following objects are in an "or" relationship. For example, A / B means: A or B.

[0050] In this article, the term "and / or" is a description of the association relationship between objects, indicating that three relationships may exist. For example, A and / or B means: A or B, or, A and B.

[0051] It should be understood that, although the various steps in the flow chart are displayed in sequence according to the indication of the arrows, these steps are not necessarily executed in sequence according to the order indicated by the arrows. Unless there is a clear description in this article, the execution of these steps is not strictly limited in order, and these steps can be executed in other orders. Moreover, at least a portion of the steps in the figure may include multiple sub-steps or multiple stages, and these sub-steps or stages are not necessarily executed at the same time, but can be executed at different times, and the execution order of these sub-steps or stages is not necessarily to be carried out in sequence, but can be executed in turn or alternately with other steps or at least a portion of the sub-steps or stages of other steps.

[0052] Each module in the device or system of the present application can be implemented in whole or in part by software, hardware, or a combination thereof. The above modules can be embedded in or independent of a processor in a computer device in the form of hardware, or can be stored in a memory in a computer device in the form of software, so that the processor can call and execute operations corresponding to the above modules.

[0053] In the absence of conflict, the embodiments of the present invention and the features of the embodiments may be combined with each other.

[0054] Fig.12 An embodiment of an optical telephone solution system of an automatic pairing communication mode of the present invention is shown.

[0055] In this optional embodiment, the optical telephone solution system with automatic pairing communication mode includes: a single-chip microcomputer control unit 201, a transmitting unit 203 and a receiving unit 205; the transmitting unit 203 is connected to the receiving unit 205, and the single-chip microcomputer control unit 201 is connected to the transmitting unit 203 and the receiving unit 205; the single-chip microcomputer control unit 201 is used to generate and identify handshake pulse signals; control the working wavelengths of the transmitting and receiving channels; adjust the output volume by controlling the digital potentiometer; the transmitting unit 203 is used to output a PWM waveform modulated by the audio signal through an audio modulation circuit, and control the constant current switch circuit and the laser module through the PWM waveform; the receiving unit 205 is used to amplify, shape and filter the photocurrent signal, and input the photocurrent signal into the single-chip microcomputer.

[0056] In this optional embodiment, the audio modulation circuit includes a preamplifier, a limiting amplifier, a triangle wave generator and a voltage comparator;

[0057] Outputting a PWM waveform modulated by an audio signal through an audio modulation circuit includes: amplifying a voltage signal from an audio acquisition device in turn through a preamplifier and a limiting amplifier, and limiting the fluctuation range of the voltage signal to a preset range; generating a triangular wave of a fixed frequency by using a triangular wave generator; connecting the voltage signal output by the limiting amplifier through the same-phase input terminal of a voltage comparator, connecting the triangular wave of a fixed frequency output by the triangular wave generator through the inverting input terminal of the voltage comparator, and outputting a PWM waveform modulated by the audio signal through the output terminal of the voltage comparator.

[0058] In this optional embodiment, the duty cycle period of the PWM waveform is the same as the period of the triangle wave output by the triangle wave generator.

[0059] In this optional embodiment, the constant current switch circuit includes a laser diode LD1, a resistor R3, a transistor Q4, a resistor R1, a MOS transistor Q2, a MOS transistor Q1, a transistor Q3, a resistor R2, a resistor R4, a resistor R6, a resistor R5, a transistor Q5, a voltage reference V1, a capacitor C1, a capacitor C2, a resistor R7, a resistor R8, a resistor R9, a resistor R10, a resistor R11, a resistor R12, a resistor R13, a resistor R14, a resistor R15, a resistor R16, a diode D1, a diode D2, a transistor Q6 and a transistor Q7; wherein the fourth end of the laser diode LD1 is connected to the third end of the MOS transistor Q2, and the first end of the MOS transistor Q2 is connected to the The first end of the transistor Q4 is connected to one end of the resistor R3, the second end of the MOS transistor Q2 is connected to the other end of the resistor R1, one end of the resistor R2 and the second end of the MOS transistor Q1 in sequence, the third end of the MOS transistor Q1 is connected to the eighth end of the laser diode LD1, the other end of the resistor R2 is connected to the first end of the MOS transistor Q1 and the second end of the transistor Q3 in sequence, the first end of the transistor Q3 is connected to one end of the resistor R4; the second end and the sixth end of the laser diode LD1 are both connected to one end of the resistor R5, the other end of the resistor R5 is connected to the second end of the transistor Q5, the first end of the transistor Q5 is connected to the One end of the resistor R6 is connected to the first end of the voltage reference V1 and the second end of the voltage reference V1, the other end of the resistor R6 is connected to one end of the capacitor C1, the other end of the capacitor C1 is sequentially connected to the third end of the voltage reference V1, one end of the resistor R10 and one end of the resistor R11, the other end of the resistor R10 is sequentially connected to the third end of the transistor Q5, the first end of the resistor R7, the third end of the resistor R8, one end of the capacitor C2 and one end of the resistor R9, the second end and the third end of the resistor R7 are connected to the other end of the resistor R11, the second end and the first end of the resistor R8 are connected to one end of the resistor R12, the other end of the resistor R12 is sequentially connected to the other end of the capacitor C2, the other end of the resistor R9 The first end of the transistor Q6 and the second end of the transistor Q7 are connected to one end, the second end of the transistor Q7 and the cathode of the diode D1 and the cathode of the diode D2, the anode of the diode D1 is connected to the first end of the transistor Q6, one end of the resistor R13, one end of the capacitor C3 and one end of the resistor R15 in sequence, the other end of the resistor R13 is connected to the other end of the capacitor C3, the other end of the resistor R15 is connected to the third end of the transistor Q6, the third end of the transistor Q7 and one end of the resistor R16 in sequence, the other end of the resistor R16 is connected to the first end of the transistor Q7, the anode of the diode D2, one end of the resistor R14 and one end of the capacitor C4 in sequence, and the other end of the resistor R14 is connected to the other end of the capacitor C4.

[0060] In this optional embodiment, transistor Q5 and voltage reference V1 form a constant current circuit; resistor R7 and resistor R8 are used to adjust the drive current and bias current of laser diode LD1.

[0061] In this optional embodiment, the photocurrent signal is amplified, shaped and filtered, and the photocurrent signal is input into the single-chip microcomputer, including: the receiving unit amplifies the photocurrent signal through a limiting transimpedance amplifier and an inverting amplifier, and uses the inverting amplifier to shape the photocurrent signal; the high-frequency carrier signal in the photocurrent signal is filtered out by a filter, and an audio signal is output; the photocurrent signal is obtained by the single-chip microcomputer, and the handshake pulse signal is recognized by the single-chip microcomputer control unit during handshake.

[0062] In this optional embodiment, the limiting transimpedance amplifier includes an optical receiving module PIN1A, a diode D21, a resistor R21, a capacitor C21, a capacitor C22, a capacitor C23, a chip U1, a resistor R23, a capacitor C24, a resistor R22, a resistor R24, a junction field effect transistor Q11 and a junction field effect transistor Q22; wherein the first end of the diode D21 is sequentially connected to one end of the resistor R21, one end of the capacitor C21, the second end of the optical receiving module PIN1A and the third end of the junction field effect transistor Q11, and the second end of the diode D21 is sequentially connected to the other end of the resistor R21, the other end of the capacitor C21 , one end of capacitor C24 is connected to the first end of chip U1, the fifth end of chip U1 is connected to one end of resistor R23, the sixth end of chip U1 is connected to one end of capacitor C23 and one end of capacitor C22 in sequence, and the other end of capacitor C23 is connected to the other end of capacitor C22; the fourth end of chip U1 is connected to one end of resistor R22 and the first end of junction field effect transistor Q22 in sequence, the other end of resistor R22 is connected to the second end of junction field effect transistor Q11, the second end of junction field effect transistor Q22 is connected to one end of resistor R24, and the other end of resistor R24 ​​is connected to the third end of junction field effect transistor Q22.

[0063] In this optional embodiment, the junction field effect transistor Q11, the junction field effect transistor Q22, the resistor R22, the resistor R24 ​​and the chip U1 form a composite amplifier, and the composite amplifier reduces the noise caused by the operational amplifier input bias current and input capacitance.

[0064] In this optional embodiment, the handshake process includes: the microcontrollers of the handshaking devices transmit audio carrier signals in a preset channel alternately at random periods; when the device on the other side continuously captures several pulses of the audio carrier signal and the signal period meets the preset requirements, the handshake is successful, and the current uplink and downlink wavelengths of the device on the other side are locked, and the device on the other side locks the opposite uplink and downlink wavelengths.

[0065] In this optional embodiment, the acquisition of the random period includes: generating a random number within a preset range based on the random noise collected by the analog-to-digital converter in combination with a random number generation algorithm, and generating a random period according to the random number.

[0066] In order to facilitate understanding of the above technical solutions of the present invention, the above technical solutions of the present invention are further described below from the perspective of architecture and principle, as follows:

[0067] The main structure of the present invention includes three parts: a single-chip control unit, a transmitting unit and a receiving unit. The transmitting unit is composed of an audio amplification and modulation part, a laser constant current drive part and a dual-wavelength laser module (1490nm, 1550nm); the receiving unit includes a dual-wavelength PIN tube module (1490nm, 1550nm), an anti-saturation transimpedance amplifier part, a signal shaping and filtering part and an audio amplification part. The internal transmitting module and the receiving module pigtails are connected to the output port through a 3db coupler. Specific block diagram, such as Fig.13 shown.

[0068] Among them, the single-chip microcomputer control circuit has three functions: 1. Generate and identify handshake pulse signals; 2. Control the working wavelength of the transmitting and receiving channels; 3. Control the digital potentiometer to adjust the output volume.

[0069] The audio modulation circuit consists of four parts: a preamplifier, a limiting amplifier, a triangle wave generator, and a voltage comparator. The preamplifier amplifies the weak voltage signal from the microphone; the limiting amplifier further amplifies the signal from the preamplifier and clamps the output signal to a maximum of 1.4Vpp (peak-to-peak voltage) to prevent distortion; the triangle wave generator generates a triangle wave of a fixed frequency; the non-inverting input of the voltage comparator is connected to the audio voltage signal from the limiting amplifier, and the inverting input is connected to the triangle wave generated by the triangle wave generator, and the output outputs a PWM wave modulated by the audio signal. Its duty cycle is controlled by the audio signal voltage at the sampling moment, and its period is the same as the triangle wave period output by the triangle wave generator. The specific block diagram is as follows: Fig.14 shown.

[0070] The PWM waveform generated by the audio modulation part controls the constant current switch circuit, controls the laser module, and the schematic diagram of the constant current circuit is as follows: Fig.15 As shown, it is mainly composed of discrete devices. Compared with the use of IC, it can accurately adjust the drive current and bias current and obtain a very high current rise / fall edge speed (≤5ns) without high total device cost. Another alternative to the PWM digital modulation method used is to use ADC (analog-to-digital converter) to sample the input audio signal, and use DSP (digital signal processor) or FPGA (field programmable gate array) to compress and encode the audio sampling signal into a bit stream, and transmit it in the form of a data packet in the optical fiber. This solution will have higher flexibility and can transmit more than just audio signals. But this solution will greatly increase the complexity of the entire system.

[0071] Among them, transistor Q5 and voltage reference V1 together form a constant current circuit, and adjusting resistors R7 and R8 can accurately adjust the drive current and bias current of the laser diode respectively. The significance of accurately adjusting the drive current is to maximize the output power of the laser diode without affecting its working life. Adjusting the bias current can eliminate the influence of the critical current of the laser diode and increase the operating frequency of the laser diode.

[0072] The receiving unit converts the weak photocurrent signal from the PIN tube into a stronger voltage signal through a limiting transimpedance amplifier, and then further amplifies it through an inverting amplifier and enters the voltage comparator to be shaped into a standard 5V level. After passing through an analog switch, it is input into the microcontroller and a low-pass filter. The signal enters the microcontroller to identify the handshake signal during handshake, and enters the low-pass filter with a cutoff frequency of 20KHz to filter out the high-frequency carrier signal and then output the audio signal. The specific block diagram is as follows: Fig.16 shown.

[0073] Among them, the limiting transimpedance amplifier uses discrete JFET (junction field effect transistor) and operational amplifier to form a composite transimpedance amplifier, and adds a diode limiting circuit to improve the circuit's overload resistance and effectively solve the problem of taking into account both large and small signals under high gain conditions. Its schematic diagram is shown in the figure below. Fig.17 shown.

[0074] Among them, the junction field effect transistor Q11, the junction field effect transistor Q22, the resistor R22, and the resistor R24 ​​form a source follower structure, and together with the operational amplifier chip U1, form a composite amplifier. This composite structure can greatly reduce the noise caused by the input bias current and input capacitance of the operational amplifier. The nonlinearity of the diode D1 introduces an additional feedback path, which is equivalent to automatically reducing the circuit gain when a large signal is input, achieving the purpose of anti-saturation.

[0075] During the handshake process, the local and remote microcontrollers transmit audio carrier signals alternately in the 1490nm and 1550nm channels with random cycles (random noise collected by ADC combined with random numbers within a specific range generated by a random number generation algorithm). At the same time, the receiving channel is detected at another wavelength to see if there is a handshake signal from the other party. If several signal pulses are captured continuously and the signal cycle meets the requirements, the program automatically switches to the handshake success state and locks the current uplink and downlink wavelengths. At the same time, the other party's device will also subsequently lock the opposite uplink and downlink wavelengths. For example: if an audio carrier signal is detected in the 1490nm channel, 1490nm is automatically locked as the local downlink wavelength, and 1550nm is the local uplink wavelength. At the same time, after the remote end detects the 1550nm uplink signal of the local end, it automatically locks 1550nm as the downlink wavelength and 1490nm as the uplink wavelength.

[0076] The purpose of the random detection period is to insert "jitter" into the handshake process to prevent the local and remote ends from entering the handshake process at the same time, which would cause the detection phases to be the same or close, resulting in the handshake process failing or taking too long.

[0077] like Fig.18 As shown in the figure, if the local and remote end enter the handshake mode at the same time or the time interval is very short, such as the curve at the far end A, then the time when the two sides detect asynchronously, that is, the handshake window time is also very short, such as the curve handshake window A. In practical applications, in order to avoid interference, it is usually necessary to continuously detect several handshake pulses before identifying the handshake as successful. Therefore, if the time window is too small, it may not be possible to continuously collect enough pulses, resulting in recognition failure. However, if a random number within a certain range is used to control the recognition cycle, this problem can be completely avoided, such as Fig.19 Among them, although the recognition period is controlled by a random number, the overall single switching period is controlled within 100ms. Therefore, compared with the fixed switching period, this control method cannot produce a periodic fixed window, but it guarantees that a certain number of long time windows can be generated under any circumstances. The long time window is more conducive to the recognition of the handshake pulse. Usually, only one long time window is needed to complete the recognition and locking of the wavelength.

[0078] The present invention includes: a digital signal modulation and demodulation circuit; a composite limiting transimpedance amplifier; and a random number jitter handshake algorithm. It solves the following shortcomings of traditional fiber-optic telephones:

[0079] 1. The uplink and downlink wavelengths are fixed, and A and B must be used in pairs. 2. Using analog modulation technology, the signal transmission distance is short, and the signal-to-noise ratio decreases significantly as the transmission distance increases. The communication distance is short and the noise is high. 3. Using analog modulation technology makes it impossible to naturally take into account both long-distance communication mode and short-distance communication mode in circuit design, and users need to switch manually, which is inflexible to use.

[0080] In addition, if Figure 2-Figure 11 middle, Figure 2 The midline segment ① and Figure 3 The middle line segment ① is connected, Figure 3 The midline segment ② and Figure 4 The middle line segment ② is connected, Figure 4 The midline segment ③ and Figure 5 The middle line segment ③ is connected; Figure 6 The midline segment ④ and Figure 7 The middle line segment ④ is connected, Figure 7 The middle line segment ⑤ and Figure 8 The middle line segment ⑤ is connected, Figure 8 The midline segment ⑥ and Fig. 9 The middle line segment ⑥ is connected, Fig. 9 The middle line segments ⑦ and ⑧ are respectively Fig.10 The middle line segment ⑦ is connected to the line segment ⑧. Fig.10 The middle line segment ⑨ and line segment ⑩ are respectively Fig.11 The middle line segment ⑨ is connected to the line segment ⑩.

[0081] The present invention is not limited to the structures which have been described above and shown in the drawings, and various modifications and changes may be made without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

Claims

1. An optical telephone solution system with automatic pairing communication mode, characterized in that: The optical telephone solution system includes: a single chip control unit, a transmitting unit and a receiving unit; The transmitting unit is connected to the receiving unit, and the single chip control unit is connected to the transmitting unit and the receiving unit; The single-chip control unit is used to generate and identify handshake pulse signals; control the working wavelengths of the transmitting and receiving channels; and adjust the output volume by controlling the digital potentiometer; The transmitting unit is used to output a PWM waveform modulated by an audio signal through an audio modulation circuit, and control a constant current switch circuit and a laser module through the PWM waveform; The receiving unit is used to amplify, shape and filter the photocurrent signal, and input the photocurrent signal into the single chip microcomputer.

2. The optical telephone solution system of the automatic pairing communication method according to claim 1 is characterized in that: The audio modulation circuit includes a preamplifier, a limiting amplifier, a triangle wave generator and a voltage comparator; The step of outputting a PWM waveform modulated by an audio signal through an audio modulation circuit comprises: The voltage signal from the audio acquisition device is amplified in sequence by the preamplifier and the limiting amplifier, and the fluctuation range of the voltage signal is limited to a preset range; The triangular wave generator is used to generate a triangular wave of a fixed frequency; the voltage signal output by the limiting amplifier is connected through the non-inverting input end of the voltage comparator, the triangular wave of a fixed frequency output by the triangular wave generator is connected through the inverting input end of the voltage comparator, and a PWM waveform modulated by an audio signal is output through the output end of the voltage comparator.

3. The optical telephone solution system of the automatic pairing communication method according to claim 2 is characterized in that: The duty cycle of the PWM waveform is the same as the period of the triangular wave output by the triangular wave generator.

4. The optical telephone solution system of the automatic pairing communication method according to claim 1 is characterized in that: The constant current switch circuit includes a laser diode LD1, a resistor R3, a transistor Q4, a resistor R1, a MOS transistor Q2, a MOS transistor Q1, a transistor Q3, a resistor R2, a resistor R4, a resistor R6, a resistor R5, a transistor Q5, a voltage reference V1, a capacitor C1, a capacitor C2, a resistor R7, a resistor R8, a resistor R9, a resistor R10, a resistor R11, a resistor R12, a resistor R13, a resistor R14, a resistor R15, a resistor R16, a diode D1, a diode D2, a transistor Q6 and a transistor Q7; The fourth end of the laser diode LD1 is connected to the third end of the MOS transistor Q2, the first end of the MOS transistor Q2 is connected to one end of the resistor R1 and the second end of the triode Q4 in sequence, the first end of the triode Q4 is connected to one end of the resistor R3, the second end of the MOS transistor Q2 is connected to the other end of the resistor R1, one end of the resistor R2 and the second end of the MOS transistor Q1 in sequence, the third end of the MOS transistor Q1 is connected to the eighth end of the laser diode LD1, the other end of the resistor R2 is connected to the first end of the MOS transistor Q1 and the second end of the triode Q3 in sequence, and the first end of the triode Q3 is connected to one end of the resistor R4; The second end and the sixth end of the laser diode LD1 are connected to one end of the resistor R5, the other end of the resistor R5 is connected to the second end of the transistor Q5, the first end of the transistor Q5 is connected to one end of the resistor R6, the first end of the voltage reference V1 and the second end of the voltage reference V1 in sequence, the other end of the resistor R6 is connected to one end of the capacitor C1, the other end of the capacitor C1 is connected to the third end of the voltage reference V1, one end of the resistor R10 and one end of the resistor R11 in sequence, the other end of the resistor R10 is connected to the third end of the transistor Q5, the first end of the resistor R7, the third end of the resistor R8, one end of the capacitor C2 and one end of the resistor R9 in sequence, the second end and the third end of the resistor R7 are connected to the other end of the resistor R11, the second end and the first end of the resistor R8 are connected to one end of the resistor R12 The other end of the resistor R12 is connected to the other end of the capacitor C2, the other end of the resistor R9, the second end of the transistor Q6, the second end of the transistor Q7, the cathode of the diode D1 and the cathode of the diode D2 in sequence. The anode of the diode D1 is connected to the first end of the transistor Q6, one end of the resistor R13, one end of the capacitor C3 and one end of the resistor R15 in sequence. The other end of the resistor R13 is connected to the other end of the capacitor C3. The other end of the resistor R15 is connected to the third end of the transistor Q6, the third end of the transistor Q7 and one end of the resistor R16 in sequence. The other end of the resistor R16 is connected to the first end of the transistor Q7, the anode of the diode D2, one end of the resistor R14 and one end of the capacitor C4 in sequence. The other end of the resistor R14 is connected to the other end of the capacitor C4.

5. The optical telephone solution system of the automatic pairing communication method according to claim 4 is characterized in that: The transistor Q5 and the voltage reference V1 form a constant current circuit; The resistor R7 and the resistor R8 are used to adjust the driving current and bias current of the laser diode LD1.

6. The optical telephone solution system of the automatic pairing communication method according to claim 1, characterized in that: The amplifying, shaping and filtering the photocurrent signal and inputting the photocurrent signal into the single chip microcomputer comprises: The receiving unit amplifies the photocurrent signal through a limiting transimpedance amplifier and an inverting amplifier, and uses the inverting amplifier to perform shaping processing on the photocurrent signal; The high-frequency carrier signal in the photocurrent signal is filtered out by a filter, and an audio signal is output; the photocurrent signal is acquired by a single-chip microcomputer, and the single-chip microcomputer control unit is used to identify a handshake pulse signal during handshake.

7. The optical telephone solution system of the automatic pairing communication method according to claim 6 is characterized in that: The limiting transimpedance amplifier includes an optical receiving module PIN1A, a diode D21, a resistor R21, a capacitor C21, a capacitor C22, a capacitor C23, a chip U1, a resistor R23, a capacitor C24, a resistor R22, a resistor R24, a junction field effect transistor Q11 and a junction field effect transistor Q22; Wherein, the first end of the diode D21 is connected to one end of the resistor R21, one end of the capacitor C21, the second end of the optical receiving module PIN1A and the third end of the junction field effect transistor Q11 in sequence, the second end of the diode D21 is connected to the other end of the resistor R21, the other end of the capacitor C21, one end of the capacitor C24 and the first end of the chip U1 in sequence, the fifth end of the chip U1 is connected to one end of the resistor R23, the sixth end of the chip U1 is connected to one end of the capacitor C23 and one end of the capacitor C22 in sequence, and the other end of the capacitor C23 is connected to the other end of the capacitor C22; The fourth end of the chip U1 is connected to one end of the resistor R22 and the first end of the junction field effect transistor Q22 in sequence, the other end of the resistor R22 is connected to the second end of the junction field effect transistor Q11, the second end of the junction field effect transistor Q22 is connected to one end of the resistor R24, and the other end of the resistor R24 ​​is connected to the third end of the junction field effect transistor Q22.

8. The optical telephone solution system of the automatic pairing communication method according to claim 7 is characterized in that: The junction field effect transistor Q11, the junction field effect transistor Q22, the resistor R22, the resistor R24 ​​and the chip U1 form a composite amplifier, and the composite amplifier reduces the noise caused by the input bias current and input capacitance of the operational amplifier.

9. The optical telephone solution system of the automatic pairing communication method according to claim 1, characterized in that: The handshake process includes: The single-chip microcomputers of the handshake devices transmit audio carrier signals in a preset channel alternately at random periods; When the local device continuously captures several pulses of the audio carrier signal and the signal period meets the preset requirements, the handshake is successful, and the current uplink and downlink wavelengths of the local device are locked, and the other device locks the opposite uplink and downlink wavelengths.

10. The optical telephone solution system of the automatic pairing communication method according to claim 9, characterized in that: The acquisition of the random cycle includes: Based on the random noise collected by the analog-to-digital converter and combined with the random number generation algorithm, a random number within a preset range is generated, and a random cycle is generated based on the random number.

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