A line and logic communication circuit based on optical fiber transmission

Abstract

This invention discloses a wired-AND logic communication circuit based on optical fiber transmission, including a first level conversion circuit, a second level conversion circuit, a first laser control circuit, a second laser control circuit, photodetectors D1a and D1b, lasers D2a and D2b, and an optical fiber transmission system. The optical fiber transmission system is used to transmit the optical signal from laser D2a to photodetector D1b and to transmit the optical signal from laser D2b to photodetector D1a. The first level conversion circuit controls the state of a first port based on the state of photodetector D1a, the second level conversion circuit controls the state of a second port based on the state of photodetector D1b, the first laser control circuit controls the state of laser D2a based on the state of photodetector D1a and the state of the first port, and the second laser control circuit controls the state of laser D2b based on the state of photodetector D1b and the state of the second port. This invention solves the problem of limited long-distance cable transmission.

Description

Technical Field

[0001] This invention relates to the field of optical communication transmission technology, and more specifically to a wired-AND logic communication circuit based on optical fiber transmission. Background Technology

[0002] Fiber optic communication boasts advantages such as high speed, low loss, low cost, interference resistance, and security and reliability, making it widely used in modern communication. While fiber optics are widely used for transmitting high-speed signals, cables are still used for transmitting some low-speed signals. However, the signal attenuates and deteriorates over longer distances, limiting long-distance transmission and restricting its application in certain scenarios, such as those where optical communication equipment widely uses I2C and SPI communication interfaces.

[0003] For example, the HDMI high-definition video transmission interface includes four high-speed channels and two low-speed channels. The high-speed channels are used to transmit high-definition video signals, and each channel requires several GHz of bandwidth; the low-speed channels are used for compatibility communication between the signal source and the display and for processing encrypted information, etc., using wired-AND logic I2C communication, with channel rates on the order of hundreds of kHz.

[0004] In ordinary households, HDMI interfaces only need to transmit a few meters using a cable. However, in some situations, such as in cinemas, 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 high-speed signals generally use fiber optic transmission. I2C signals can also be transmitted over distances of tens to hundreds of meters using wires by means of raising the level and equalization, but there is no advantage in terms of cost and performance for longer distances.

[0006] Unlike HDMI, where the high-speed channel uses NRZ signals to achieve fiber optic communication simply by transmitting and receiving laser signals, I2C communication uses wired-AND logic. Simply connecting two ports using laser transmission and reception cannot complete wired-AND logic communication. Summary of the Invention

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

[0008] The technical solution of this invention is implemented as follows: This invention discloses a wired-AND logic communication circuit based on optical fiber transmission, including a first level conversion circuit, a second level conversion circuit, a first laser control circuit, a second laser control circuit, as well as photodetectors D1a, D1b, lasers D2a and D2b, and an optical fiber transmission system. The optical fiber transmission system is used to transmit the optical signal generated by laser D2a to photodetector D1b and to transmit the optical signal generated by laser D2b to photodetector D1a. The first level conversion circuit is used to control the state of a first port according to the state of photodetector D1a. The second level conversion circuit is used to control the state of a second port according to the state of photodetector D1b. The first laser control circuit is used to control the state of laser D2a according to the state of photodetector D1a and the state of the first port. The second laser control circuit is used to control the state of laser D2b according to the state of photodetector D1b and the state of the second port.

[0009] Furthermore, the negative terminal of photodetector D1a is connected to one end of resistor R2a, the other end of resistor R2a is connected to voltage VCC, and the positive terminal of photodetector D1a is grounded.

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

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

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

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

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

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

[0016] Furthermore, the first logic circuit includes a first AND gate circuit, the first input terminal of the first AND gate circuit is connected to the collector of transistor Q2a, the second input terminal of the first AND gate circuit is connected to the negative terminal of photodetector D1a, and the output terminal of the first AND gate circuit is connected to the positive terminal of laser D2a.

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

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

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

[0020] Furthermore, the fiber optic-based wired-AND logic communication circuit of the present invention also includes current-limiting resistors R5a and R5b, with current-limiting resistor R5a connected in series with laser D2a and current-limiting resistor R5b connected in series with laser D2b.

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

[0022] Furthermore, the optical fiber transmission system includes a first optical fiber and a second optical fiber. Laser D2a is connected to photodetector D1b through the first optical fiber, and laser D2b is connected to photodetector D1a through the second optical fiber.

[0023] or,

[0024] The optical fiber transmission system includes a single optical fiber, with beam splitters installed at both ends of the optical fiber to achieve multiplexing of transmission and reception.

[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 method that cannot be transmitted over long distances based on cables, and provides a wired-and-logic communication circuit based on optical fiber transmission. The present invention utilizes a circuit logic conversion to complete communication between two wired-and-logic ports using optical fiber. This circuit can realize optical fiber communication using wired-and-logic interfaces such as I2C and SPI.

[0028] This invention uses optical fiber transmission, which is low-loss, low-weight, low-cost, and highly reliable, and can achieve long-distance transmission.

[0029] This invention uses optical fiber to achieve wired logic transmission, which is not limited by the transmission distance of cables. This method is not limited to I2C and can be extended to communication methods such as SPI and MDIO. Attached Figure Description

[0030] Figure 1 A circuit diagram of a fiber optic-based wired-and-logic communication circuit provided in one embodiment of the present invention;

[0031] Figure 2 This is a schematic diagram of the logical relationships between nodes in a fiber optic-based wired-AND logic communication circuit, provided as an embodiment of the present invention. Detailed Implementation

[0032] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0033] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, the terms "an," "a," or "the" do not indicate a quantity limitation, but rather indicate the presence of at least one. The terms "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. The terms "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. "Up," "down," "left," "right," etc., are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0034] In the various figures, the same elements are represented by similar reference numerals. For clarity, not all parts in the figures are drawn to scale. Furthermore, some well-known parts may not be shown in the figures.

[0035] Many specific details of the invention, such as the structure, materials, dimensions, processing methods, and techniques of the components, are described below to provide a clearer understanding of the invention. However, as those skilled in the art will understand, the invention may be implemented without following these specific details.

[0036] See Figure 1 This invention provides a wired-AND logic communication circuit based on optical fiber transmission, including a first level conversion circuit, a second level conversion circuit, a first laser control circuit, a second laser control circuit, photodetectors D1a and D1b, lasers D2a and D2b, and an optical fiber transmission system. The optical fiber transmission system is used to transmit optical signals generated by laser D2a to photodetector D1b and to transmit optical signals generated by laser D2b to photodetector D1a. The first level conversion circuit is used to control the state (level) of a first port according to the state of photodetector D1a. The second level conversion circuit is used to control the state (level) of a second port according to the state of photodetector D1b. The first laser control circuit is used to control the state of laser D2a according to the state of photodetector D1a and the state (level) of the first port. The second laser control circuit is used to control the state of laser D2b according to the state of photodetector D1b and the 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 for SDA or SCL.

[0038] When photodetector D1a is in the ON state, the first port is at a low level. When photodetector D1a is in the OFF state, the first port is at a high level.

[0039] When photodetector D1b is in the ON state, the second port is at a low level. When photodetector D1b is in the OFF state, the second port is at a high level.

[0040] Furthermore, the negative terminal of photodetector D1a is connected to one end of resistor R2a, the other end of resistor R2a is connected to voltage VCC, and the positive terminal of photodetector D1a is grounded.

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

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

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

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

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

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

[0047] Furthermore, the first logic circuit adopts a first AND gate circuit. The first input terminal of the first AND gate circuit is connected to the collector of transistor Q2a, the second input terminal of the first AND gate circuit is connected to the negative terminal of photodetector D1a, and the output terminal of the first AND gate circuit is connected to the positive terminal of laser D2a.

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

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

[0050] Furthermore, if the output capability of the logic circuit is insufficient, additional driving elements are needed to enhance the output current.

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

[0052] A second driving element is provided between the output terminal of the second AND gate circuit and the positive terminal of the laser D2b. The second driving element is used to receive the signal from the second logic circuit and convert it into the 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 fiber optic-based wired-AND logic communication circuit of the present invention also includes current-limiting resistors R5a and R5b, with current-limiting resistor R5a connected in series with laser D2a and current-limiting resistor R5b connected in series with laser D2b.

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

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

[0057] Figure 1 The two dashed lines with arrows represent optical fibers, connecting the laser and detector at either end. There are many ways to implement an optical fiber transmission system to transmit the optical signal generated by laser D2a to photodetector D1b, and vice versa.

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

[0059] In some embodiments, the optical fiber transmission system includes a single optical fiber, with beam splitters at both ends to achieve multiplexing of transmission and reception. This embodiment uses a single optical fiber, with beam splitters at both ends for multiplexing of transmission and reception.

[0060] In some embodiments, the optical fiber transmission system employs an optical fiber wavelength division multiplexing (WDM) system. This embodiment uses a single optical fiber and different wavelength lasers to achieve WDM technology.

[0061] This invention provides a circuit for communication between interfaces such as I2C and SPI via optical fiber transmission, 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. When one wire is low, the entire bus is low. This invention can utilize optical fiber to implement the wired-AND logic of I2C, and use optical fiber transmission to connect the AO and BO ports, such as... Figure 1 The circuit diagram shows that the first port AO and the second port BO are two communication ports for SDA or SCL (generally, the output is an open collector structure). A and B represent the line status (high level or low level) outside ports AO and BO. The circuit, optical transceiver, and optical fiber in the dashed box realize a virtual cable connection between points A and B. R1a and R1b are pull-up resistors for the I2C bus. Both the SDA and SCL buses are processed in this way.

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

[0064] Initially, A0 and B0 outputs are high, according to Figure 1 The circuit logic is as follows: when PDA and PDB are high, neither laser emits light, and both PDA and PDB are at a high level. The changing logic states are described as follows:

[0065] When the output of port B0 goes low, according to Figure 1 The circuit logic is as follows: Node B is low → LDB goes high → Laser B emits light → Detector A receives light and conducts → PDA is pulled low → Transistor Q1a conducts → 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 The table lists various output changes for ports AO and BO. It can be seen that the wired-AND logic relationship A = B = AO and BO is satisfied under all conditions.

[0067] When one of the A0 and B0 terminals is low, the A and B bus levels are low. When both A0 and B0 terminals are high, A and B are high. Depending on the actual application, unnecessary logic can be handled in software design.

[0068] This invention uses optical fiber transmission, which is low-loss, lightweight, low-cost, and highly reliable, and can achieve long-distance transmission. Optical fiber enables wired logic transmission, which is not limited by the transmission distance of cables. This method is not limited to I2C and can be extended to communication methods such as SPI and MDIO.

[0069] It is understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled 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 wired-AND logic communication circuit based on optical fiber transmission, characterized in that... The system includes a first port AO, a second port BO, a first level conversion circuit, a second level conversion circuit, a first laser control circuit, a second laser control circuit, photodetectors D1a and D1b, lasers D2a and D2b, and an optical fiber transmission system. The optical fiber transmission system is used to transmit the optical signal generated by laser D2a to photodetector D1b and to transmit the optical signal generated by laser D2b to photodetector D1a. The first level conversion circuit is used to control the state of the first port according to the state of photodetector D1a. The second level conversion circuit is used to control the state of the second port according to the state of photodetector D1b. The first laser control circuit is used to control the state of laser D2a according to the state of photodetector D1a and the state of the first port. The second laser control circuit is used to control the state of laser D2b according to the state of photodetector D1b and the state of the second port. The first port AO and the second port BO are the communication ports of the line and logic bus; When either port AO or port BO is low, the line and logic bus are at a low level. When both port AO and port BO are high, the line and logic bus are at a high level.

2. The wired-AND logic communication circuit based on optical fiber transmission as described in claim 1, characterized in that: The negative terminal of photodetector D1a is connected to one end of resistor R2a, the other end of resistor R2a is connected to voltage VCC, and the positive terminal of photodetector D1a is grounded. The negative terminal of photodetector D1b is connected to one end of resistor R2b, the other end of resistor R2b is connected to voltage VCC, and the positive terminal of photodetector D1b is grounded.

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

4. The wired-AND logic communication circuit based on optical fiber transmission as described in claim 3, characterized in that: Transistors Q1a and Q1b are PNP transistors.

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

6. The wired-AND logic communication circuit based on optical fiber transmission as described in claim 1, characterized in that: The first logic circuit includes a first AND gate circuit. The first input terminal of the first AND gate circuit is connected to the collector of transistor Q2a, the second input terminal of the first AND gate circuit is connected to the negative terminal of photodetector D1a, and the output terminal of the first AND gate circuit is connected to the positive terminal of laser D2a. The second logic circuit includes a second AND gate circuit. The first input terminal of the second AND gate circuit is connected to the collector of transistor Q2b, the second input terminal of the second AND gate circuit is connected to the negative terminal of photodetector D1b, and the output terminal of the second AND gate circuit is connected to the positive terminal of laser D2b.

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

8. The fiber-optic-based wired-AND logic communication circuit as described in claim 5, 6, or 7, characterized in that: It also includes current-limiting resistors R5a and R5b, with current-limiting resistor R5a connected in series with laser D2a and current-limiting resistor R5b connected in series with laser D2b.

9. The wired-AND logic communication circuit based on optical fiber transmission as described in claim 5, characterized in that: Transistors Q2a and Q2b are NPN transistors.

10. The wired-AND logic communication circuit based on optical fiber transmission as described in claim 1, characterized in that: The optical fiber transmission system includes a first optical fiber and a second optical fiber. Laser D2a is connected to photodetector D1b through the first optical fiber, and laser D2b is connected to photodetector D1a through the second optical fiber. or, The optical fiber transmission system includes a single optical fiber, with beam splitters installed at both ends of the optical fiber to achieve multiplexing of transmission and reception. or, The optical fiber transmission system adopts an optical fiber wavelength division multiplexing system.

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