A signal transmission method and an optical module

Abstract

The application discloses a signal transmission method and an optical module. The optical module comprises a receiving end for receiving a first signal and a second signal; a transmitting end circuit for processing and transmitting the first signal and the second signal; the receiving end circuit comprises a photoelectric detector for receiving a signal transmitted by the transmitting end circuit, a transimpedance amplifier for converting an output signal of the photoelectric detector into a voltage signal, a first output branch for limiting and outputting an output signal of the transimpedance amplifier, a mirror circuit for mirroring an RSSI current signal of the transimpedance amplifier, and a second output branch for processing an output current of the mirror circuit to resolve the second signal. The frequency of the first signal is greater than the low-frequency cutoff frequency of the transimpedance amplifier, and the frequency of the second signal is less than the low-frequency cutoff frequency of the transimpedance amplifier. The optical module can simultaneously transmit high-frequency signals and low-frequency signals without needing two optical modules, and has a small packaging space.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of signal transmission, and particularly relates to a signal transmission method and an optical module. BACKGROUND

[0002] The transmission rate of the current optical module is mainly 155 Mb / s, 622 Mb / s, 1.25 Gb / s, 3.125 Gb / s, 6 Gb / s, 10 Gb / s, 25 Gb / s, etc. The compatible rate of an optical module is usually 155 Mb / s-3.125 Gb / s, 1.25 Gb / s-10.3 Gb / s, 1.25 Gb / s-25 Gb / s, etc. At present and in a long time to come, the modules mainly used for data signal transmission or the optical modules with higher rate will continue to be produced at home and abroad.

[0003] Since optical fiber transmission has replaced electrical signal transmission, it is inevitable to require some control signals and data signals to be transmitted through optical fibers. This requires the optical module to be capable of simultaneously transmitting data signals of 1.25 Gb / s-10.3 Gb / s and control signals of 1Khz-100Khz. However, the existing high-speed transmission optical module cannot simultaneously transmit high-speed data signals of 1.25 Gb / s-10.3 Gb / s and low-frequency control signals of 1Khz-100Khz due to the low-frequency bandwidth cutoff of the transimpedance amplifier at the optical receiving end, especially in the case of low-frequency rate <50Khz.

[0004] The conventional solution for transmitting high-speed signals and low-speed signals is to use two optical modules to respectively transmit high-speed signals of 1.25 Gb / s-10.3 Gb / s and low-speed signals of 1Khz-100Khz.

[0005] The existing above-mentioned method has the following problems: the use of two optical modules to simultaneously transmit high-speed signals and low-speed signals has high cost and large packaging space. SUMMARY

[0006] In order to solve the problem that the existing optical module cannot simultaneously transmit high-speed signals and low-speed signals due to the low-frequency bandwidth cutoff of the transimpedance amplifier, the present application provides a signal transmission method and an optical module, which can simultaneously transmit high-frequency signals and low-frequency signals without the need for two optical modules and has small packaging space.

[0007] The purpose of the present application is achieved by the following technical solutions:

[0008] The present application provides an optical module in a first aspect, comprising:

[0009] a signal receiving end, the signal receiving end comprising a first signal receiving end for receiving a first signal and a second signal receiving end for receiving a second signal;

[0010] a transmitting end circuit, which processes the first and second signals and transmits them;

[0011] a receiving end circuit, which comprises a photodetector for receiving the signals transmitted by the transmitting end circuit, a transimpedance amplifier for converting the output signal of the photodetector into a voltage signal, a first output branch for limiting the output signal of the transimpedance amplifier, a mirror circuit for mirroring the RSSI current signal of the transimpedance amplifier, and a second output branch for processing the output current of the mirror circuit to resolve the second signal, the frequency of the first signal being greater than the low-frequency cutoff frequency of the transimpedance amplifier, and the frequency of the second signal being less than the low-frequency cutoff frequency of the transimpedance amplifier.

[0012] In a possible design, the transmitting end circuit comprises:

[0013] a first driving circuit for filtering the first signal;

[0014] a second driving circuit for filtering the second signal;

[0015] an optical transmitting unit for transmitting the output signals of the first and second driving circuits.

[0016] In a possible design, the second driving circuit comprises a first signal processing circuit for excluding the AC signal of the second signal receiving end, and an adjusting circuit for adjusting the voltage intensity of the output of the first signal processing circuit.

[0017] In a possible design, the second output branch comprises a emitter follower for converting the RSSI current signal of the photodetector into a voltage signal, a coupling capacitor for coupling the signal output end signal of the emitter follower, and a signal amplification circuit for amplifying the coupling voltage of the coupling capacitor.

[0018] In a possible design, the second output branch further comprises a second signal processing circuit connected at the output end of the signal amplification circuit to shield noise signals.

[0019] In a possible design, the second signal processing circuit comprises a comparator and a voltage dividing circuit connected at one input end of the comparator.

[0020] In a possible design, the output end of the emitter follower is connected with an optical power sampling circuit.

[0021] The second aspect of the present application provides a signal transmission method, comprising the following steps:

[0022] acquire a first signal and a second signal, the frequency of the first signal being greater than a critical frequency, the frequency of the second signal being less than the critical frequency;

[0023] filter the first signal and the second signal and then transmit the filtered signals;

[0024] receive the first signal and the second signal by using a photoelectric detector;

[0025] convert the output signal of the photoelectric detector into a voltage signal by using a trans-impedance amplifier, then perform amplitude limiting output to resolve the first signal, and simultaneously resolve the second signal according to the change of the RSSI current of the trans-impedance amplifier, the critical frequency being the low-frequency cutoff frequency of the trans-impedance amplifier.

[0026] Compared with the prior art, the present application has at least the following advantages and beneficial effects:

[0027] The scheme of the present application realizes signal transmission by using one optical fiber, resolves high-speed signals by using a trans-impedance amplifier and a first output branch, resolves low-speed signals by using the change of the RSSI current of the photoelectric detector, realizes the transmission of high-speed and low-speed signals simultaneously by using one optical fiber, and reduces the packaging space. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0029] Figure 1 the schematic diagram of the optical module of the present application;

[0030] Figure 2 the circuit diagram of the first signal processing part in a specific example of the present application;

[0031] Figure 3 the circuit diagram of the second signal transmitting part in a specific example of the present application;

[0032] Figure 4 the circuit diagram of the second signal receiving part in a specific example of the present application;

[0033] Figure 5 the circuit schematic diagram and pin relationship in a specific example of the present application. DETAILED DESCRIPTION

[0034] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some but not all of the embodiments of the present application. Generally, the components of the embodiments of the present application described and shown in the drawings can be arranged and designed in various different configurations.

[0035] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of the application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0036] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0037] It should be noted that: similar reference numerals and letters indicate similar items in the following drawings, therefore, once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings.

[0038] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship commonly placed when the product of the present application is used, or the orientation or positional relationship commonly understood by the person skilled in the art, and are only for the convenience of describing the present application and simplifying the description, and are not intended to indicate or imply that the indicated device or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second" and the like are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0039] In the description of the present application, it should also be noted that, unless otherwise explicitly specified and limited, the terms "arrangement", "installation", "connection", "connection" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be the communication inside two elements. For a person of ordinary skill in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0040] The transmitting end circuit and the receiving end circuit of the existing optical module are respectively based on a laser and a photodetector. The laser is used for transmitting an optical signal, and the photodetector is used for converting the optical signal transmitted by the laser through an optical fiber into an electrical signal. The optical signal output by the photodetector is amplified and output through a transimpedance amplifier. Since the transimpedance amplifier has a low-frequency cutoff frequency, the frequency of the signal amplified based on the transimpedance amplifier is greater than the low-frequency cutoff frequency of the transimpedance amplifier. To solve the problem that the optical module based on the transimpedance amplifier can only transmit signals greater than the low-frequency cutoff frequency of the transimpedance amplifier, as shown in the prior art, the present application discloses an optical module, which comprises a signal receiving end, a transmitting end circuit and a receiving end circuit. Figure 1

[0041] The signal receiving end comprises a first signal receiving end for receiving a first signal and a second signal receiving end for receiving a second signal. The first signal is a high-speed signal, and the frequency of the first signal is greater than the low-frequency cutoff frequency of the transimpedance amplifier. The first signal can be a CML signal, a PECL signal, an ECL signal, an LVDS signal, etc. The second signal is a low-speed signal, and the frequency of the second signal is less than the low-frequency cutoff frequency of the transimpedance amplifier. The second signal can be a control signal TTL, an RS232 interface level, etc. The transmitting end circuit processes and transmits the first signal and the second signal. The receiving end circuit comprises a photodetector for receiving the signal transmitted by the transmitting end circuit, a transimpedance amplifier for converting the output signal of the photodetector into a voltage signal, a first output branch for limiting the output signal of the transimpedance amplifier, a mirror circuit for mirroring the RSSI current signal of the transimpedance amplifier, and a second output branch for processing the output current of the mirror circuit to analyze the second signal.

[0042] The present application adds a second output branch to the receiving end circuit, processes the RSSI current of the photodetector through the second output branch to analyze the low-speed second signal, and only needs a single optical fiber to realize the transmission of high-speed and low-speed signals, thereby simplifying the circuit structure and reducing the requirement for the packaging area.

[0043] Based on the above principle, specifically, the transmitting end circuit comprises a first driving circuit for filtering and processing the first signal, a second driving circuit for filtering and processing the second signal, and an optical transmitting unit for transmitting the output signals of the first driving circuit and the second driving circuit. The optical transmitting unit is the laser mentioned above.

[0044] In order to facilitate the light emitting power of the optical transmitting unit, i.e. the laser, the second driving circuit comprises a first signal processing circuit for isolating the alternating current signal of the second signal receiving end and an adjusting circuit for adjusting the voltage intensity of the output of the first signal processing circuit.

[0045] ​Specifically, the second output branch includes an emitter follower for converting the RSSI current signal of the photodetector into a voltage signal, a coupling capacitor for coupling the signal output end of the emitter follower, and a signal amplification circuit for amplifying the coupling voltage of the coupling capacitor.

[0046] Based on the above-mentioned second output branch structure, in order to shield some stray noise signals, a second signal processing circuit for shielding noise signals is connected at the output end of the signal amplification circuit. Specifically, the second signal processing circuit includes a comparator and a voltage dividing circuit connected to an input end of the comparator. The threshold voltage is set by the voltage dividing circuit to shield stray noise signals.

[0047] In order to facilitate the detection of abnormal installation of the optical link, an optical power sampling circuit is connected at the output end of the emitter follower. Specifically, the optical power sampling circuit can also be realized by a voltage dividing circuit.

[0048] For example, referring to Figures 2 to 5 , in this example, the first signal is CML; the second signal is TTL.

[0049] For high-speed data of CML, as shown in Figure 2 , the first signal receiving end TD+, TD-, chip U1 is GN1157 or EOC5002, the part of the structure of chip U1, chip U3 and the circuit between pin 17, pin 16 of chip U1 and chip U3 constitute the first driving circuit, which realizes the shaping and filtering of the first signal and then sends it to the LD+, LD- of the laser TOSA. The laser TOSA emits modulated light. Chip U4 integrates photodetector, transimpedance amplifier and mirror circuit. After ROSA receives the optical data signal and converts it into an electrical signal, it is processed by the first output branch composed of capacitor C17, capacitor C16 and the limiting amplifier of chip U1, and then the CML signal is sent to the first signal output port RD+, RD- through pin 2, pin 2 of chip U1, thereby completing the closed-loop transmission of the entire CML level photoelectric conversion transmission.

[0050] For low-speed control signals of TTL signals:

[0051] As shown in Figure 3As shown, the second signal receiving end EncoderIn, chip U5 is a high-speed switch, chip U5, inductance L1, L2, L4, L5 constitute the first signal processing circuit; the adjusting circuit includes chip U2 and its peripheral circuit, chip U2 constitutes a positive feedback circuit, the output voltage intensity of the first signal processing circuit is adjusted. When EncoderIn is high, the pin5 foot of chip U5 is high, at this time the LD- of the laser is high, the laser LD has no new current flowing through, that is, the laser light power is unchanged. When EncoderIn is low, the pin5 foot of chip U5 is low, at this time the LD- of the laser is low, the laser LD has new current flowing through, that is, the laser light power is changed. Through the change of LD light power, the TTL signal of EncoderIn can be emitted in the form of light. AOP_DAC modulates the change of laser LD light power. By controlling the input voltage of AOP_DAC, the output voltage of chip U2 Pin4 foot can be controlled, so as to control the size of LD new current. The input range of AOP_DAC is 0~2.5V, the output voltage of chip U2 Pin4 foot is 0~3.75V, and the control output should be limited to less than 1.5V to avoid the laser not emitting light completely, because at this time the high-speed CML alternating current signal must be loaded on the laser which is continuously emitting light.

[0052] The mirror circuit is integrated in chip U4, and the RSSI current is output through pin7 foot. Figure 4 As shown, chip U7 and its peripheral circuit constitute an emitter follower, which converts the RSSI current signal into a voltage signal output from pin4 foot, and the change part of pin4 foot voltage, that is, the alternating component, is coupled to pin1 foot of chip U6 through coupling capacitor C6. Chip U6 and its peripheral circuit amplify the coupling voltage of the coupling capacitor. In this embodiment, chip U6 is a positive feedback circuit, which realizes 200 times amplification of the input signal of pin1 foot and then outputs.

[0053] Chip U8, capacitor C4, inductance L8, resistor R21 and resistor R27 constitute the second signal processing circuit. Among them, chip U8 is a comparator, and resistor R21 and resistor R27 constitute a voltage divider circuit. The signal of pin4 foot of chip U6 is input to pin4 foot of U8, and then compared with the threshold voltage of pin3 foot of U8, and finally EncoderOut is output from pin1 foot of U8. Among them, R27 and R21 are used to set the threshold voltage, which is generally recommended to be set to 50mV or 100mV to shield some stray noise signals.

[0054] The resistance R15 and the resistance R22 constitute a light power sampling circuit.

[0055] Through the above example, the structure of the tube optical module and its pin interface are shown as Figure 5 The meanings of the pins are shown in Table 1.

[0056] Table 1

[0057]

[0058] TD+ / TD- High-speed 1~10.3125G data input signal, which is a CML level.

[0059] RD+ / RD- High-speed 1~10.3125G data output signal, which is a CML level.

[0060] EncoderIn Low-speed 1Khz~100Khz control input signal, which is a TTL level.

[0061] EncoderIn Low-speed 1Khz~100Khz control output signal, which is a TTL level.

[0062] Of course, the example in the present scheme is only for the purpose of illustrating the present scheme so as to facilitate the understanding of the present scheme, and does not constitute a limitation of the present scheme.

[0063] Since the high-speed CML signal passes through the ROSA, the generated RSSI current is constant, so the change of the EncoderIn causes the change of the LD light emitting power, and further causes the change of the RSSI current of the receiving light detector. The change of the RSSI current is captured to restore the EncoderIn TTL signal loaded on the LD.

[0064] Through the above scheme, compared with the two optical modules used to realize the transmission of low-speed signals and high-speed signals, only one module can complete the functions of two optical modules in the traditional scheme, and the cost is reduced by about 50%.

[0065] Based on the principle and any one structure of the optical module in the first aspect, the second aspect of the present application discloses a signal transmission method, comprising steps S01 to S04.

[0066] Step S01, acquiring a first signal and a second signal, the frequency of the first signal being greater than a critical frequency, and the frequency of the second signal being less than the critical frequency.

[0067] Step S02, transmitting after filtering the first signal and the second signal.

[0068] Step S03, receiving the first signal and the second signal by using a photoelectric detector.

[0069] Step S04, converting the output signal of the photoelectric detector into a voltage signal by using a transimpedance amplifier, then performing amplitude limiting output to resolve the first signal, and resolving the second signal according to the RSSI current size change of the transimpedance amplifier, wherein the critical frequency is the low frequency cutoff frequency of the transimpedance amplifier.

[0070] The specific implementation method of each step of the method disclosed in the second aspect of the present application can be referred to the first aspect, which will not be repeated here.

[0071] Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacements to part of the technical features, and any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. An optical module characterized by comprising: include: The signal receiving end includes a first signal receiving end for receiving a first signal and a second signal receiving end for receiving a second signal; A transmitting circuit that processes and transmits the first and second signals; The receiving circuit includes a photodetector for receiving signals transmitted by the transmitting circuit, a transimpedance amplifier for converting the output signal of the photodetector into a voltage signal, a first output branch for limiting the output signal of the transimpedance amplifier, a mirror circuit for mirroring the RSSI current signal of the transimpedance amplifier, and a second output branch for processing the output current of the mirror circuit to extract the second signal. The frequency of the first signal is greater than the low-frequency cutoff frequency of the transimpedance amplifier, and the frequency of the second signal is less than the low-frequency cutoff frequency of the transimpedance amplifier.

2. An optical module according to claim 1, characterized in that The transmitting circuit includes: A first driving circuit for filtering the first signal; A second driving circuit for filtering the second signal; A light emitting unit used to transmit the output signals of the first driving circuit and the second driving circuit.

3. An optical module according to claim 2, wherein The second driving circuit includes a first signal processing circuit for isolating AC signals from the second signal receiving end and an adjustment circuit for adjusting the output voltage intensity of the first signal processing circuit.

4. The optical module of claim 1, wherein The second output branch includes an emitter follower for converting the RSSI current signal of the photodetector into a voltage signal, a coupling capacitor for coupling the signal output of the emitter follower, and a signal amplification circuit for amplifying the coupling voltage of the coupling capacitor.

5. An optical module according to claim 4, wherein The second output branch also includes a second signal processing circuit connected to the output of the signal amplification circuit to shield noise signals.

6. An optical module according to claim 5, characterized in that: The second signal processing circuit includes a comparator and a voltage divider circuit connected to one input terminal of the comparator.

7. The optical module of claim 4, wherein: The output of the emitter follower is connected to an optical power sampling circuit.

8. A signal transmission method characterized by, Includes the following steps: Acquire a first signal and a second signal, wherein the frequency of the first signal is greater than a critical frequency and the frequency of the second signal is less than the critical frequency; The first and second signals are filtered before being transmitted. A photodetector is used to receive the first and second signals; The output signal of the photodetector is converted into a voltage signal by a transimpedance amplifier and then the output is limited to extract the first signal. At the same time, the second signal is extracted based on the change in the RSSI current of the transimpedance amplifier. The critical frequency is the low-frequency cutoff frequency of the transimpedance amplifier.

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