Line and logic communication circuit based on optical fiber transmission

Abstract

The invention discloses a line AND logic communication circuit based on optical fiber transmission, which comprises a first level conversion circuit, a second level conversion circuit, a first laser control circuit, a second laser control circuit, an optical detector D1a, an optical detector D1b, a laser D2a, a laser D2b and an optical fiber transmission system, the optical fiber transmission system is used for transmitting an optical signal of the laser D2a to the optical detector D1b and transmitting an optical signal of the laser D2b to the optical detector D1a, the first level conversion circuit is used for controlling the state of the first port according to the state of the optical detector D1a, and the second level conversion circuit is used for controlling the state of the second port according to the state of the optical detector D1b. The first laser control circuit is used for controlling the state of the laser D2a according to the state of the optical detector D1a and the state of the first port, and the second laser control circuit is used for controlling the state of the laser D2b according to the state of the optical detector D1b and the state of the second port. The problem that long-distance cable transmission is limited is solved.

Description

Technical Field

[0001] The present invention relates to the field of optical communication transmission technology, and more specifically to a line and logic communication circuit based on optical fiber transmission. Background Art

[0002] Optical fiber communication has the advantages of high speed, low loss, low cost, anti-interference, safety and reliability, so it is widely used in the field of modern communications. Many high-speed signals have been transmitted by optical fiber, while some low-speed signals are still transmitted by cables. As the transmission distance of the cable increases, the signal will attenuate and deteriorate, and long-distance transmission cannot be achieved. It is limited in some application scenarios, such as the application scenarios of I2C, SPI and other communication interfaces widely used in optical communication equipment.

[0003] For example, the HDMI high-definition video transmission interface contains four high-speed channels and two low-speed channels. The high-speed channel is used to transmit high-definition video signals, and each channel requires a bandwidth of several GHz; the low-speed channel is used to communicate the compatibility between the signal source and the display and process encryption information, etc., using the I2C communication of line and logic, and the channel rate is in the hundreds of KHz level.

[0004] Ordinary households only need to transmit a few meters using cables when using the HDMI interface, but in some occasions, such as in theaters, the signal source is often tens or hundreds of meters away from the projection equipment, and some advertising display applications even require transmission over longer distances.

[0005] In these applications, HDMI's high-speed signals are generally transmitted using optical fiber, and I2C signals can be transmitted over distances of tens to hundreds of meters using wires by means of pulling up the level and equalization, but longer distances do not have advantages in terms of cost and performance.

[0006] Unlike HDMI, where the high-speed channel uses NRZ signals and can simply achieve optical fiber communication through laser transmission and reception, I2C communication uses wired logic. Simply using laser transmission and reception to connect two ports cannot achieve wired logic communication. Summary of the invention

[0007] The present invention aims to solve at least one of the technical problems existing in the prior art, and proposes a line-and-logic communication circuit based on optical fiber transmission. The present invention utilizes a circuit logic conversion to complete communication between two line-and-logic ports using optical fiber. This circuit can realize optical fiber communication using line-and-logic interfaces such as I2C and SPI.

[0008] The technical solution of the present invention is implemented as follows: The present invention discloses a line-and-logic communication circuit based on optical fiber transmission, comprising a first level conversion circuit, a second level conversion circuit, a first laser control circuit, a second laser control circuit, a light detector D1a, a light detector D1b, a laser D2a, a laser D2b and an optical fiber transmission system, wherein the optical fiber transmission system is used to transmit the optical signal generated by the laser D2a to the light detector D1b and to transmit the optical signal generated by the laser D2b to the light detector D1a, the first level conversion circuit is used to control the state of the first port according to the state of the light detector D1a, the second level conversion circuit is used to control the state of the second port according to the state of the light detector D1b, the first laser control circuit is used to control the state of the laser D2a according to the state of the light detector D1a and the state of the first port, and the second laser control circuit is used to control the state of the laser D2b according to the state of the light detector D1b and the state of the second port.

[0009] Further, the cathode of the photodetector D1a is connected to one end of the resistor R2a, the other end of the resistor R2a is connected to the voltage VCC, and the anode of the photodetector D1a is grounded;

[0010] The cathode of the photodetector D1b is connected to one end of the resistor R2b, the other end of the resistor R2b is connected to the voltage VCC, and the anode of the photodetector D1b is grounded.

[0011] Further, the first level conversion circuit includes a transistor Q1a, the emitter of the transistor Q1a is connected to one end of the resistor R1a and the first port respectively, the other end of the resistor R1a is connected to the voltage VCC, the collector of the transistor Q1a is grounded, and the base of the transistor Q1a is connected to the negative electrode of the photodetector D1a;

[0012] The second level conversion circuit includes a transistor Q1b, the emitter of which is connected to one end and the second port of the resistor R1b respectively, the other end of the resistor R1b is connected to the voltage VCC, the collector of the transistor Q1b is grounded, and the base of the transistor Q1b is connected to the negative electrode of the photodetector D1b.

[0013] Furthermore, the transistor Q1a and the transistor Q1b are PNP transistors.

[0014] Further, the first laser control circuit includes a transistor Q2a and a first logic circuit, the base of the transistor Q2a is connected to the first port directly or via a resistor R3a, the emitter of the transistor Q2a is grounded, the collector of the transistor Q2a is respectively connected to one end of the resistor R4a and the first input end of the first logic circuit, the other end of the resistor R4a is connected to a voltage VCC, the second input end of the second logic circuit is connected to the negative electrode of the photodetector D1a, the output end of the first logic circuit is connected to the positive electrode of the laser D2a, and the negative electrode of the laser D2a is grounded;

[0015] The second laser control circuit includes a transistor Q2b and a second logic circuit, the base of the transistor Q2b is connected to the second port directly or via a resistor R3b, the emitter of the transistor Q2b is grounded, the collector of the transistor Q2b is respectively connected to one end of the resistor R4b and the first input end of the second logic circuit, the other end of the resistor R4b is connected to a voltage VCC, the second input end of the second logic circuit is connected to the cathode of the photodetector D1b, the output end of the second logic circuit is connected to the anode of the laser D2b, and the cathode of the laser D2b is grounded.

[0016] Further, the first logic circuit includes a first AND gate circuit, a first input end of the first AND gate circuit is connected to the collector of the transistor Q2a, a second input end of the first AND gate circuit is connected to the cathode of the photodetector D1a, and an output end of the first AND gate circuit is connected to the anode of the laser D2a;

[0017] The second logic circuit includes a second AND gate circuit, a first input end of the second AND gate circuit is connected to the collector of transistor Q2b, a second input end of the second AND gate circuit is connected to the cathode of photodetector D1b, and an output end of the second AND gate circuit is connected to the anode of laser D2b.

[0018] Furthermore, a first driving element is provided between the output end of the first AND gate circuit and the positive electrode of the laser D2a, and the first driving element is used to receive the signal from the first logic circuit and convert it into a required current to drive the laser D2a;

[0019] A second driving element is provided between the output end of the second AND gate circuit and the positive electrode of the laser D2b. The second driving element is used to receive a signal from the second logic circuit and convert it into a required current to drive the laser D2b.

[0020] Furthermore, the line and logic communication circuit based on optical fiber transmission of the present invention further includes a current limiting resistor R5a and a current limiting resistor R5b. The current limiting resistor R5a is connected in series with the laser D2a, and the current limiting resistor R5b is connected in series with the laser D2b.

[0021] Furthermore, the transistor Q2a and the transistor Q2b are NPN transistors.

[0022] Further, the optical fiber transmission system includes a first optical fiber and a second optical fiber, the laser D2a is connected to the optical detector D1b through the first optical fiber, and the laser D2b is connected to the optical detector D1a through the second optical fiber;

[0023] or,

[0024] The optical fiber transmission system comprises an optical fiber, and optical splitters are arranged at both ends of the optical fiber to realize transmission and reception multiplexing;

[0025] or,

[0026] The optical fiber transmission system adopts an optical fiber wavelength division multiplexing system.

[0027] Compared with the prior art, the present invention has the following beneficial effects: the present invention optimizes the communication mode based on cables that cannot transmit over long distances, and provides a line-and-logic communication circuit based on optical fiber transmission. The present invention utilizes a circuit logic conversion to complete communication between two line-and-logic ports using optical fiber. This circuit can realize optical fiber communications using line-and-logic interfaces such as I2C and SPI.

[0028] The present invention adopts optical fiber transmission, which has low loss, low weight, low cost, high reliability, and can realize long-distance transmission;

[0029] The present invention uses optical fiber to realize line and logic transmission, which is not limited by the transmission distance limit of the cable. This method is not limited to I2C, and can be extended to SPI, MDIO and other communication methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A circuit diagram of a line and logic communication circuit based on optical fiber transmission provided by an embodiment of the present invention;

[0031] Figure 2 A schematic diagram of the logical relationship between a line and nodes in a logic communication circuit based on optical fiber transmission provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0032] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0033] Unless otherwise defined, the technical terms or scientific terms used in the present invention should be understood by people with ordinary skills in the field to which the present invention belongs. The "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. Similarly, similar words such as "one", "one" or "the" do not indicate quantity restrictions, but indicate that there is at least one. Similar words such as "include" or "comprise" mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Similar words such as "connect" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described target changes, the relative positional relationship may also change accordingly.

[0034] In each of the accompanying drawings, identical elements are represented by similar reference numerals. For the sake of clarity, the various parts in the accompanying drawings are not all drawn to scale. In addition, some well-known parts may not be shown in the drawings.

[0035] Many specific details of the present invention are described below, such as component structures, materials, dimensions, processing techniques and technologies, in order to more clearly understand the present invention. However, as those skilled in the art will appreciate, the present invention may be implemented without following these specific details.

[0036] See also Figure 1 An embodiment of the present invention provides a line-and-logic communication circuit based on optical fiber transmission, comprising a first level conversion circuit, a second level conversion circuit, a first laser control circuit, a second laser control circuit, a light detector D1a, a light detector D1b, a laser D2a, a laser D2b and an optical fiber transmission system, wherein the optical fiber transmission system is used to transmit an optical signal generated by the laser D2a to the light detector D1b and to transmit an optical signal generated by the laser D2b to the light detector D1a, wherein the first level conversion circuit is used to control a state (level) of a first port according to a state of the light detector D1a, wherein the second level conversion circuit is used to control a state (level) of a second port according to a state of the light detector D1b, wherein the first laser control circuit is used to control a state of the laser D2a according to a state of the light detector D1a and a state (level) of the first port, wherein the second laser control circuit is used to control a state of the laser D2b according to a state of the light detector D1b and a state (level) of the second port.

[0037] The first port and the second port are two wired AND logic ports, such as two communication ports of SDA or SCL.

[0038] When the light detector D1a is in the on state, the first port is at a low level. When the light detector D1a is in the off state, the first port is at a high level.

[0039] When the light detector D1b is in the on state, the second port is at a low level. When the light detector D1b is in the off state, the second port is at a high level.

[0040] Further, the cathode of the photodetector D1a is connected to one end of the resistor R2a, the other end of the resistor R2a is connected to the voltage VCC, and the anode of the photodetector D1a is grounded;

[0041] The cathode of the photodetector D1b is connected to one end of the resistor R2b, the other end of the resistor R2b is connected to the voltage VCC, and the anode of the photodetector D1b is grounded.

[0042] Further, the first level conversion circuit includes a transistor Q1a, the emitter of the transistor Q1a is connected to one end of the resistor R1a and the first port respectively, the other end of the resistor R1a is connected to the voltage VCC, the collector of the transistor Q1a is grounded, and the base of the transistor Q1a is connected to the negative electrode of the photodetector D1a;

[0043] The second level conversion circuit includes a transistor Q1b, the emitter of which is connected to one end and the second port of the resistor R1b respectively, the other end of the resistor R1b is connected to the voltage VCC, the collector of the transistor Q1b is grounded, and the base of the transistor Q1b is connected to the negative electrode of the photodetector D1b.

[0044] Furthermore, the transistor Q1a and the transistor Q1b are PNP transistors.

[0045] Further, the first laser control circuit includes a transistor Q2a and a first logic circuit, the base of the transistor Q2a is connected to the first port directly or via a resistor R3a, the emitter of the transistor Q2a is grounded, the collector of the transistor Q2a is respectively connected to one end of the resistor R4a and the first input end of the first logic circuit, the other end of the resistor R4a is connected to a voltage VCC, the second input end of the second logic circuit is connected to the negative electrode of the photodetector D1a, the output end of the first logic circuit is connected to the positive electrode of the laser D2a, and the negative electrode of the laser D2a is grounded;

[0046] The second laser control circuit includes a transistor Q2b and a second logic circuit, the base of the transistor Q2b is connected to the second port directly or via a resistor R3b, the emitter of the transistor Q2b is grounded, the collector of the transistor Q2b is respectively connected to one end of the resistor R4b and the first input end of the second logic circuit, the other end of the resistor R4b is connected to a voltage VCC, the second input end of the second logic circuit is connected to the cathode of the photodetector D1b, the output end of the second logic circuit is connected to the anode of the laser D2b, and the cathode of the laser D2b is grounded.

[0047] Further, the first logic circuit adopts a first AND gate circuit, the first input end of the first AND gate circuit is connected to the collector of the transistor Q2a, the second input end of the first AND gate circuit is connected to the cathode of the photodetector D1a, and the output end of the first AND gate circuit is connected to the anode of the laser D2a;

[0048] The second logic circuit uses a second AND gate circuit, a first input end of the second AND gate circuit is connected to the collector of transistor Q2b, a second input end of the second AND gate circuit is connected to the cathode of photodetector D1b, and an output end of the second AND gate circuit is connected to the anode of laser D2b.

[0049] The first logic circuit U1a and the second logic circuit U1b should have the output capability to directly drive the lasers D2a and D2b (usually 3mA is sufficient), otherwise a driving element needs to be added.

[0050] Furthermore, if the output capability of the logic circuit is insufficient, in this case, additional driving elements need to be added to enhance the output current.

[0051] For example, a first driving element is provided between the output end of the first AND gate circuit and the positive electrode of the laser D2a, and the first driving element is used to receive a signal from the first logic circuit and convert it into a required current to drive the laser D2a;

[0052] A second driving element is provided between the output end of the second AND gate circuit and the positive electrode of the laser D2b. The second driving element is used to receive a signal from the second logic circuit and convert it into a required current to drive the laser D2b.

[0053] The driving element can be a transistor, MOSFET or other type of current amplifier.

[0054] Furthermore, the line and logic communication circuit based on optical fiber transmission of the present invention further includes a current limiting resistor R5a and a current limiting resistor R5b. The current limiting resistor R5a is connected in series with the laser D2a, and the current limiting resistor R5b is connected in series with the laser D2b.

[0055] Furthermore, the transistor Q2a and the transistor Q2b are NPN transistors.

[0056] According to the practical application, the present invention can optimize the circuit performance by adjusting R5a, R5b, R4a, R4b, R3a, R3b, R2a, R2b, R1a, and R1b, wherein R1a and R1b are pull-up resistors of the I2C bus; R3a and R3b are transistor emitter current limiting resistors; and R5a and R5b are current limiting resistors of lasers D2a and D2b.

[0057] Figure 1 The two dotted lines with arrows in the figure represent optical fibers, which connect the laser and the detector at both ends. There are many ways to implement the optical fiber transmission system to transmit the optical signal generated by the laser D2a to the optical detector D1b and to transmit the optical signal generated by the laser D2b to the optical detector D1a:

[0058] In some embodiments, the optical fiber transmission system includes a first optical fiber and a second optical fiber, the laser D2a is connected to the optical detector D1b through the first optical fiber, and the laser D2b is connected to the optical detector D1a through the second optical fiber. This embodiment uses two optical fibers, each of which is connected to the laser on one side and the detector on the other side.

[0059] In some embodiments, the optical fiber transmission system includes an optical fiber, and optical splitters are arranged at both ends of the optical fiber to realize multiplexing of transmission and reception. This embodiment uses an optical fiber, and optical splitters are used at both ends to multiplex transmission and reception.

[0060] In some embodiments, the optical fiber transmission system adopts an optical fiber wavelength division multiplexing system. This embodiment adopts one optical fiber and uses lasers of different wavelengths to implement WDM (wavelength division multiplexing) technology.

[0061] The present invention realizes a circuit for communication between interfaces such as I2C and SPI through optical fiber transmission, thereby solving the problem of limited long-distance cable transmission.

[0062] The I2C bus uses a two-wire serial bus, namely SDA and SCL, both of which are wired AND logic. If one of the bus lines is low, the bus line is low. The present invention can use optical fiber transmission to realize the wired AND logic of I2C, and use optical fiber transmission to realize the connection between the two ports AO to BO, such as Figure 1 As shown in the circuit: the first port AO and the second port BO are two communication ports of SDA or SCL (generally open collector structure when outputting), A and B represent the line status (high level or low level) outside the AO port and the BO port, the circuit, optical transceiver device, optical fiber, etc. in the virtual frame realize the virtual cable connection between point A and point B, R1a, R1b are the pull-up resistors of the I2C bus. Both SDA and SCL buses are processed in this way.

[0063] For this design, the states of ports A and B satisfy the line-and logic. Considering bidirectional transmission, the possible logical states are as follows: Figure 2 shown.

[0064] In the initialization state, A0 and B0 outputs are high level. Figure 1 The circuit logic, PDA, PDB are high, both lasers are not emitting light, PDA and PDB are both high level, the changing logic state is described as follows:

[0065] When the B0 port output becomes low, according to Figure 1 The circuit logic is that the B node is low → LDB becomes high → laser B emits light → detector A receives light and turns on → PDA is pulled low → transistor Q1a turns on → A is pulled low; A is low, PDA is low → LDA does not emit light → detector B remains without receiving light → PDB remains high...

[0066] Figure 2 Various output changes of ports AO and BO are listed in FIG. 1 . It can be seen that the line-AND logic relationship of A=B=AOand BO is satisfied under various conditions.

[0067] When one of A0 and B0 is low, the A and B bus levels are low. When both A0 and B0 are high, A and B are high. According to the actual application, the unnecessary logic can be processed by software design.

[0068] The present invention adopts optical fiber transmission, which has low loss, low weight, low cost, high reliability, and can realize long-distance transmission; optical fiber realizes line and logic transmission, and is not limited by the transmission distance limit of the cable. This method is not limited to I2C, and can be extended to SPI, MDIO and other communication methods.

[0069] It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present invention, but the present invention is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A line and logic communication circuit based on optical fiber transmission, characterized in that : includes a first level conversion circuit, a second level conversion circuit, a first laser control circuit, a second laser control circuit, a light detector D1a, a light detector D1b, a laser D2a, a laser D2b and an optical fiber transmission system, wherein the optical fiber transmission system is used to transmit the optical signal generated by the laser D2a to the light detector D1b and to transmit the optical signal generated by the laser D2b to the light detector D1a, the first level conversion circuit is used to control the state of the first port according to the state of the light detector D1a, the second level conversion circuit is used to control the state of the second port according to the state of the light detector D1b, the first laser control circuit is used to control the state of the laser D2a according to the state of the light detector D1a and the state of the first port, and the second laser control circuit is used to control the state of the laser D2b according to the state of the light detector D1b and the state of the second port.

2. The line and logic communication circuit based on optical fiber transmission as claimed in claim 1, characterized in that: The cathode of the photodetector D1a is connected to one end of the resistor R2a, the other end of the resistor R2a is connected to the voltage VCC, and the anode of the photodetector D1a is grounded; The cathode of the photodetector D1b is connected to one end of the resistor R2b, the other end of the resistor R2b is connected to the voltage VCC, and the anode of the photodetector D1b is grounded.

3. The line and logic communication circuit based on optical fiber transmission as claimed in claim 2, characterized in that: The first level conversion circuit includes a transistor Q1a, the emitter of the transistor Q1a is connected to one end of the resistor R1a and the first port respectively, the other end of the resistor R1a is connected to the voltage VCC, the collector of the transistor Q1a is grounded, and the base of the transistor Q1a is connected to the negative electrode of the photodetector D1a; The second level conversion circuit includes a transistor Q1b, the emitter of which is connected to one end and the second port of the resistor R1b respectively, the other end of the resistor R1b is connected to the voltage VCC, the collector of the transistor Q1b is grounded, and the base of the transistor Q1b is connected to the negative electrode of the photodetector D1b.

4. The line and logic communication circuit based on optical fiber transmission as claimed in claim 3, characterized in that: The transistor Q1a and the transistor Q1b are PNP transistors.

5. The line and logic communication circuit based on optical fiber transmission as claimed in claim 2, characterized in that: The first laser control circuit includes a transistor Q2a and a first logic circuit, the base of the transistor Q2a is connected to the first port directly or via a resistor R3a, the emitter of the transistor Q2a is grounded, the collector of the transistor Q2a is connected to one end of the resistor R4a and the first input end of the first logic circuit respectively, the other end of the resistor R4a is connected to a voltage VCC, the second input end of the second logic circuit is connected to the negative electrode of the photodetector D1a, the output end of the first logic circuit is connected to the positive electrode of the laser D2a, and the negative electrode of the laser D2a is grounded; The second laser control circuit includes a transistor Q2b and a second logic circuit, the base of the transistor Q2b is connected to the second port directly or via a resistor R3b, the emitter of the transistor Q2b is grounded, the collector of the transistor Q2b is respectively connected to one end of the resistor R4b and the first input end of the second logic circuit, the other end of the resistor R4b is connected to a voltage VCC, the second input end of the second logic circuit is connected to the cathode of the photodetector D1b, the output end of the second logic circuit is connected to the anode of the laser D2b, and the cathode of the laser D2b is grounded.

6. The line and logic communication circuit based on optical fiber transmission as claimed in claim 1, characterized in that: The first logic circuit includes a first AND gate circuit, a first input end of the first AND gate circuit is connected to the collector of the transistor Q2a, a second input end of the first AND gate circuit is connected to the cathode of the photodetector D1a, and an output end of the first AND gate circuit is connected to the anode of the laser D2a; The second logic circuit includes a second AND gate circuit, a first input end of the second AND gate circuit is connected to the collector of transistor Q2b, a second input end of the second AND gate circuit is connected to the cathode of photodetector D1b, and an output end of the second AND gate circuit is connected to the anode of laser D2b.

7. The line and logic communication circuit based on optical fiber transmission as claimed in claim 6, characterized in that: A first driving element is provided between the output end of the first AND gate circuit and the positive electrode of the laser D2a, and the first driving element is used to receive a signal from the first logic circuit and convert it into a required current to drive the laser D2a; A second driving element is provided between the output end of the second AND gate circuit and the positive electrode of the laser D2b. The second driving element is used to receive a signal from the second logic circuit and convert it into a required current to drive the laser D2b.

8. The line and logic communication circuit based on optical fiber transmission as claimed in claim 5, 6 or 7, characterized in that: The device also includes a current limiting resistor R5a and a current limiting resistor R5b. The current limiting resistor R5a is connected in series with the laser D2a, and the current limiting resistor R5b is connected in series with the laser D2b.

9. The line and logic communication circuit based on optical fiber transmission as claimed in claim 5, characterized in that: The transistor Q2a and the transistor Q2b are NPN transistors.

10. The line and logic communication circuit based on optical fiber transmission as claimed in claim 1, characterized in that: The optical fiber transmission system includes a first optical fiber and a second optical fiber, the laser D2a is connected to the optical detector D1b through the first optical fiber, and the laser D2b is connected to the optical detector D1a through the second optical fiber; or, The optical fiber transmission system comprises an optical fiber, and optical splitters are arranged at both ends of the optical fiber to realize transmission and reception multiplexing; or, The optical fiber transmission system adopts an optical fiber wavelength division multiplexing system.

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