A wideband analog optical transmission apparatus

Abstract

The utility model relates to optical terminal technology field, concretely relates to a wide frequency band analog optical transmission equipment, including optical transmitter, optical fiber and optical receiver, and optical transmitter and optical receiver are connected through optical fiber signal, and optical transmitter is provided with signal receiving interface, input signal processing module and laser diode that electrically connect gradually, and input signal processing module includes impedance matching circuit, signal amplification circuit and drive circuit that electrically connect gradually, and drive circuit amplifies signal and drives laser diode to send laser based on base voltage division type emitter bias circuit, in the utility model, drive circuit adopts base voltage division type emitter bias circuit, and forms base voltage division network through resistance R5 and resistance R6, can stabilize the base potential of triode Q1 at fixed value, is not influenced by temperature change, at the same time, forms direct current negative feedback mechanism, effectively offsets the influence of temperature to static working point, avoids the work point drift.

Description

Technical Field

[0001] This utility model relates to the field of optical transceiver technology, specifically to a broadband analog optical transmission device. Background Technology

[0002] With the increasing demand for real-time and high-frequency adaptability of signal transmission in fields such as communications, security, and industrial control, optical transmission equipment has become a core transmission carrier due to the advantages of low loss and resistance to electromagnetic interference of optical fiber. The core working logic of optical transmission equipment is "electro-optical conversion - optical fiber transmission - photoelectric conversion": the optical transmitter converts the external electrical signal into an optical signal, which is then transmitted over long distances via optical fiber. The optical receiver then converts the optical signal back into an electrical signal for output, completing the closed loop of the link.

[0003] Currently, optical transmission equipment is mainly divided into two categories: digital and analog. Digital optical transmission equipment needs to first quantize the analog signal into a digital code stream through A / D conversion, and then perform optical modulation and transmission. Although it has strong anti-interference capabilities and supports error checking, it suffers from encoding delay and has a complex circuit structure and high cost. Analog optical transmission equipment, on the other hand, directly processes and modulates the analog electrical signal without the need for quantization and encoding. It has the advantages of strong real-time performance, simple circuit, and controllable cost, and is more suitable for scenarios with zero tolerance for delay.

[0004] The utility model patent with publication number CN208723906U discloses a high-frequency analog signal photoelectric conversion device, including an optical transmitter and an optical receiver connected to the optical transmitter; the optical transmitter is used to process the input pulse signal to generate an optical signal; the optical receiver is used to process the transmitted optical signal to output a pulse signal.

[0005] Although this utility model effectively realizes an optical transmission device capable of transmitting EMP pulse signals with bandwidths from 0.1KHz to 125MHz by placing specific optical transmitters and receivers in a shielded housing, and has a perfect housing shielding structure, the static operating point in its driving circuit is easily affected by temperature fluctuations, leading to unstable laser diode driving current, causing optical power drift, and ultimately resulting in distortion of analog signal transmission. Utility Model Content

[0006] The purpose of this invention is to provide a broadband analog optical transmission device to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, this utility model provides the following technical solution: A broadband analog optical transmission device includes an optical transmitter, an optical fiber, and an optical receiver. The optical transmitter and the optical receiver are connected by the optical fiber. The optical transmitter is provided with a signal receiving interface, an input signal processing module, and a laser diode connected in sequence. The input signal processing module includes an impedance matching circuit, a signal amplification circuit, and a driving circuit connected in sequence. The driving circuit amplifies the signal based on a base-divided emitter bias circuit and drives the laser diode to emit laser light. The optical receiver is provided with a photodetector, an output signal processing module, and a signal output interface connected in sequence. The laser diode and the photodetector are respectively disposed at both ends of the optical fiber. The output signal processing module includes a preamplifier, a main amplifier, and a filter connected in sequence.

[0008] Preferably, the impedance matching circuit includes a resistor R1, with the first end of the resistor R1 connected to the output terminal of the signal receiving interface and the second end of the resistor R1 grounded. Preferably, the signal amplification circuit includes a capacitor C1, a resistor R2, a resistor R3, a resistor R4, a capacitor C2, and an operational amplifier U1. The first terminal of capacitor C1 is connected to the first terminal of resistor R1, the second terminal of capacitor C1 is connected to the first terminal of resistor R2, the second terminal of resistor R2 is connected to the non-inverting input terminal of operational amplifier U1, the first terminal of resistor R3 is grounded, the second terminal of resistor R3 is connected to the inverting input terminal of operational amplifier U1, the first terminal of resistor R4 is connected to the inverting input terminal of operational amplifier U1, the second terminal of resistor R4 is connected to the output terminal of operational amplifier U1, the first terminal of capacitor C2 is connected to the first terminal of resistor R4, and the second terminal of capacitor C2 is connected to the second terminal of resistor R4. Preferably, the driving circuit includes a power supply VCC, resistors R5, R6, R7, and R8, and transistor Q1, wherein transistor Q1 is an NPN transistor. The first terminal of resistor R5 is connected to power supply VCC, and the second terminal of resistor R5 is connected to the output terminal of operational amplifier U1. The first terminal of resistor R6 is connected to the second terminal of resistor R5, and the second terminal of resistor R6 is grounded. The first terminal of resistor R7 is connected to power supply VCC, and the second terminal of resistor R7 is connected to the collector of transistor Q1. The base of transistor Q1 is connected to the second terminal of resistor R5. The emitter of transistor Q1 is connected to the first terminal of resistor R8, and the second terminal of resistor R8 is grounded. The second terminal of resistor R7 is also connected to the input terminal of the laser diode. These three settings form a complete process optimization from signal input, amplification to drive conversion, which simplifies the circuit structure, improves the device's adaptability to wideband analog signals and transmission stability, and effectively reduces the impact of various interference factors on signal transmission.

[0009] Compared with the prior art, the beneficial effects of this utility model are: In this invention, the driving circuit adopts a base voltage divider emitter bias circuit. Resistors R5 and R6 form a base voltage divider network, which can stabilize the base potential of transistor Q1 at a fixed value, unaffected by temperature changes. At the same time, a DC negative feedback mechanism is formed. When the temperature rises, causing the transistor current amplification factor to increase and the collector current to rise abnormally, the emitter current increases accordingly, causing the emitter voltage to rise, thereby reducing the base-emitter voltage, suppressing the base current in the reverse, and finally pulling the collector current back to a stable value. The same principle applies when the temperature decreases, effectively offsetting the influence of temperature on the static operating point and avoiding operating point drift. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of the overall structure of this utility model; Figure 2 This is a schematic diagram of the optical transmitter in this utility model; Figure 3 This is a schematic diagram of the input signal processing module in this utility model; Figure 4 This is a circuit schematic diagram of the input signal processing module in this utility model; Figure 5 This is a schematic diagram of the optical receiver in this utility model; Figure 6 This is a schematic diagram of the output signal processing module in this utility model; In the picture: 100. Optical transmitter; 101. Signal receiving interface; 102. Input signal processing module; 1020. Impedance matching circuit; 1021. Signal amplification circuit; 1022. Driver circuit; 103. Laser diode; 200. Fiber optic cable; 300. Optical receiver; 301. Photodetector; 302. Output signal processing module; 3020. Preamplifier; 3021. Main amplifier; 3022. Filter; 303. Signal output interface. Detailed Implementation

[0011] The technical solutions of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0012] Please see Figures 1-6 The present invention provides the following technical solution: A broadband analog optical transmission device includes an optical transmitter 100, an optical fiber 200, and an optical receiver 300. The optical transmitter 100 and the optical receiver 300 are connected by the optical fiber 200. The optical transmitter 100 is provided with a signal receiving interface 101, an input signal processing module 102, and a laser diode 103, which are electrically connected in sequence. The input signal processing module 102 includes an impedance matching circuit 1020, a signal amplification circuit 1021, and a driving circuit 1022, which are electrically connected in sequence. The driving circuit 1022 amplifies the signal based on a base voltage divider emitter bias circuit and drives the laser diode 103 to emit laser light. The optical receiver 300 is provided with a photodetector 301, an output signal processing module 302, and a signal output interface 303, which are electrically connected in sequence. The photodiode 103 and photodetector 301 are respectively disposed at both ends of the optical fiber 200. The output signal processing module 302 includes a preamplifier 3020, a main amplifier 3021, and a filter 3022 connected in sequence. The filter 3022 is a low-pass filter. The external broadband analog electrical signal (such as the high-frequency signal in communication and security scenarios) first enters the device through the signal receiving interface 101 of the optical transmitter 100, and then flows into the impedance matching circuit 1020 of the input signal processing module 102. After impedance matching, the electrical signal enters the signal amplification circuit 1021. The DC component is first isolated by capacitor C1, retaining only the AC analog signal. Then, it passes through the in-phase amplification circuit composed of operational amplifier U1 and resistors R2, R3, and R4. At the same time, capacitor C2... A resistor R4 is connected in parallel to filter out high-frequency noise introduced during amplification, ensuring the signal maintains linear characteristics within a wide bandwidth. The amplified electrical signal enters the driver circuit 1022, where a base voltage divider network composed of resistors R5 and R6 stabilizes the base potential of transistor Q1. The driver signal controls transistor Q1 to conduct, causing the power supply VCC to output a stable current through resistor R7, driving laser diode 103. The optical signal emitted by laser diode 103 is transmitted over a long distance through optical fiber 200. After reaching optical receiver 300, it is received by photodetector 301, which inversely converts the optical signal into a weak analog electrical signal. The weak electrical signal enters the output signal processing module 302, where it is amplified by preamplifier 3020 and main amplifier 3021. Finally, it is filtered by filter 3022 to remove noise introduced during transmission and amplification, and finally output through signal output interface 303, completing the full-link signal conversion.

[0013] In this embodiment, please refer to Figures 2-4 The impedance matching circuit 1020 includes a resistor R1. The first end of the resistor R1 is connected to the output terminal of the signal receiving interface 101, and the second end of the resistor R1 is grounded. The matching resistor of a common video signal line is 75 ohms, which reduces the reflection loss of the signal at the transmission interface and improves the signal transmission efficiency.

[0014] Specifically, the signal amplification circuit 1021 includes capacitor C1, resistor R2, resistor R3, resistor R4, capacitor C2, and operational amplifier U1. The first terminal of capacitor C1 is connected to the first terminal of resistor R1, the second terminal of capacitor C1 is connected to the first terminal of resistor R2, the second terminal of resistor R2 is connected to the non-inverting input terminal of operational amplifier U1, the first terminal of resistor R3 is grounded, the second terminal of resistor R3 is connected to the inverting input terminal of operational amplifier U1, the first terminal of resistor R4 is connected to the inverting input terminal of operational amplifier U1, and the second terminal of resistor R4 is connected to the output terminal of operational amplifier U1. The first terminal of capacitor C2 is connected to the first terminal of resistor R4, and the second terminal of capacitor C2 is connected to the second terminal of resistor R4. Capacitor C1 is used to block DC and pass AC, and is used to isolate the DC component in the input signal. Capacitor C2 is used to filter out high-frequency noise in the feedback loop. Operational amplifier U1, resistor R2, resistor R3, and resistor R4 constitute a proportional amplifier circuit. The amplification factor is determined by resistor R3 and resistor R4. Operational amplifier U1 is a low-temperature drift amplifier.

[0015] Furthermore, the drive circuit 1022 includes a power supply VCC, resistors R5, R6, R7, and R8, and a transistor Q1, which is an NPN transistor. Resistor R5 has its first terminal connected to power supply VCC and its second terminal connected to the output of operational amplifier U1. Resistor R6 has its first terminal connected to the second terminal of resistor R5, and its second terminal grounded. Resistor R7 has its first terminal connected to power supply VCC and its second terminal connected to the collector of transistor Q1. The base of transistor Q1 is connected to the second terminal of resistor R5, and the emitter of transistor Q1 is connected to the first terminal of resistor R8, whose second terminal is grounded. The second terminal of resistor R7 is also connected to the input of laser diode 103. The base voltage divider network formed by resistors R5 and R6 stabilizes the base potential of transistor Q1 at a fixed value, unaffected by temperature changes. Resistor R8 and transistor Q1 form a DC negative feedback mechanism, which can suppress base current fluctuations in the reverse direction when the temperature changes, avoiding static operating point drift. Ultimately, this ensures the stability of the drive current of laser diode 103 and reduces optical power drift.

[0016] When using the broadband analog optical transmission device of this utility model, taking a common video signal as an example, the video signal is a common broadband signal. The camera collects the analog video signal on site and transmits it to the signal receiving interface 101 of the optical transmitter 100 to complete the initial signal access. The signal flows into the impedance matching circuit 1020 of the input signal processing module 102 through the signal receiving interface 101, and impedance matching is achieved through resistor R1 (to adapt to the 75-ohm transmission standard of video signals), reducing the signal reflection loss at the interface. The signal after impedance matching enters the signal amplification circuit 1021. First, the DC component is isolated by capacitor C1, retaining only the AC video signal. Then, it is linearly amplified by the in-phase amplification circuit composed of operational amplifier U1 and resistors R2, R3, and R4. Capacitor C2 and resistor R4 are connected in parallel to filter out high-frequency noise, ensuring the linearity of the signal in a wide bandwidth. The amplified signal enters the driver circuit 1022. The base voltage divider network formed by resistors R5 and R6 stabilizes the base potential of transistor Q1. Resistor R8 and transistor Q1 form a DC negative feedback mechanism to avoid static operating point drift caused by temperature. The drive signal controls transistor Q1 to conduct, and the power supply VCC outputs a stable current through resistor R7 to drive laser diode 103. The current output by the driving circuit 1022 keeps the laser diode in a forward bias state (meeting the basic bias requirements for light emission from semiconductor devices). When the current reaches the threshold current of the laser diode, the charge carriers in its PN junction will undergo stimulated emission, directly triggering laser emission. The current output by the driving circuit 1022 is not a fixed value, but changes synchronously with the analog electrical signal input from the front end. When the amplitude of the analog electrical signal increases, the output current increases, and the optical power of the laser diode 103 increases accordingly. When the amplitude of the analog electrical signal decreases, the output current decreases, and the optical power also decreases synchronously, thus allowing the optical signal emitted by the laser diode 103 to accurately correspond to the characteristics of the input electrical signal. The laser diode 103 converts the processed analog electrical signal into an optical signal, which is then transmitted over a long distance without distortion through the optical fiber 200 and finally arrives at the optical receiver 300. The photodetector 301 of the optical receiver 300 receives the optical signal transmitted by the optical fiber 200 and reverses it to restore it into a weak analog electrical signal. The weak electrical signal enters the output signal processing module 302, is first initially amplified by the preamplifier 3020, and then further enhanced by the main amplifier 3021. The preamplifier 3020 uses low-noise amplification devices (such as low-noise operational amplifiers and field-effect transistors), and the main amplifier 3021 uses a high-gain linear amplifier circuit (such as a combination of multi-stage operational amplifiers). Finally, the filter 3022 filters out the noise introduced during transmission and amplification. The processed stable analog video signal is output through the signal output interface 303 and transmitted to the display screen, completing the full-link transmission and display of video data.

[0017] The foregoing has shown and described the basic principles, main features, and advantages of this utility model. Those skilled in the art should understand that this utility model is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the utility model. Various changes and modifications can be made to this utility model without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed utility model. The scope of protection of this utility model is defined by the appended claims and their equivalents.

Claims

1. A broadband analog optical transmission device, comprising an optical transmitter (100), an optical fiber (200), and an optical receiver (300), characterized in that: The optical transmitter (100) and the optical receiver (300) are connected by an optical fiber (200). The optical transmitter (100) is provided with a signal receiving interface (101), an input signal processing module (102), and a laser diode (103) connected in sequence. The input signal processing module (102) includes an impedance matching circuit (1020), a signal amplification circuit (1021), and a driving circuit (1022) connected in sequence. The driving circuit (1022) is based on a base voltage divider emitter bias. The circuit amplifies the signal and drives the laser diode (103) to emit laser light. The optical receiver (300) is provided with a photodetector (301), an output signal processing module (302) and a signal output interface (303) connected in sequence. The laser diode (103) and the photodetector (301) are respectively located at both ends of the optical fiber (200). The output signal processing module (302) includes a preamplifier (3020), a main amplifier (3021) and a filter (3022) connected in sequence.

2. The broadband analog optical transmission device according to claim 1, characterized in that: The impedance matching circuit (1020) includes a resistor R1, the first end of which is connected to the output terminal of the signal receiving interface (101), and the second end of which is grounded.

3. The broadband analog optical transmission device according to claim 2, characterized in that: The signal amplification circuit (1021) includes capacitor C1, resistor R2, resistor R3, resistor R4, capacitor C2, and operational amplifier U1. The first terminal of capacitor C1 is connected to the first terminal of resistor R1, the second terminal of capacitor C1 is connected to the first terminal of resistor R2, the second terminal of resistor R2 is connected to the non-inverting input terminal of operational amplifier U1, the first terminal of resistor R3 is grounded, the second terminal of resistor R3 is connected to the inverting input terminal of operational amplifier U1, the first terminal of resistor R4 is connected to the inverting input terminal of operational amplifier U1, the second terminal of resistor R4 is connected to the output terminal of operational amplifier U1, the first terminal of capacitor C2 is connected to the first terminal of resistor R4, and the second terminal of capacitor C2 is connected to the second terminal of resistor R4.

4. The broadband analog optical transmission device according to claim 3, characterized in that: The driving circuit (1022) includes a power supply VCC, resistors R5, R6, R7, and R8, and a transistor Q1, which is an NPN transistor. The first end of resistor R5 is connected to power supply VCC, the second end of resistor R5 is connected to the output terminal of operational amplifier U1, the first end of resistor R6 is connected to the second end of resistor R5, the second end of resistor R6 is grounded, the first end of resistor R7 is connected to power supply VCC, the second end of resistor R7 is connected to the collector of transistor Q1, the base of transistor Q1 is connected to the second end of resistor R5, the emitter of transistor Q1 is connected to the first end of resistor R8, the second end of resistor R8 is grounded, and the second end of resistor R7 is also connected to the input terminal of the laser diode (103).

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