Multipath MPD light current monitoring circuit

Abstract

The utility model provides a multipath MPD photocurrent monitoring circuit, the monitoring circuit comprises a multipath MPD monitoring circuit, an analog switch, a transimpedance amplification circuit and a selective welding resistance circuit, the analog switch comprises a moving end and a fixed end, the moving end of the analog switch is connected with a plurality of MPD tubes of the multipath MPD monitoring circuit, and the fixed end of the analog switch is connected with the MPD tubes of the multipath MPD monitoring circuit. The fixed end of the analog switch is connected with the selective welding resistance circuit, the common electrode of the multi-path MPD monitoring circuit is connected with the selective welding resistance circuit, and the selective welding resistance circuit is connected with the transimpedance amplification circuit. The fixed end of the analog switch is only communicated with one of the movable ends at the same time, the selective welding resistance circuit is a loop formed by sequentially connecting four resistance devices in series, and the common-cathode multi-path MPD and the common-anode multi-path MPD can share the same light current monitoring circuit in a welding and missing welding mode. One PCB is compatible with two silicon optical chips with different designs, and two sets of PCBs do not need to be designed for different silicon optical chips, so that the development cost is greatly reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of communication, in particular to a multi-channel MPD photocurrent monitoring circuit. Background Art

[0002] Optical fiber communication technology has the advantages of fast speed, large bandwidth, no interference, high density and low power consumption, and has become the mainstream in long-distance high-speed communication. Optical interconnection technology and optoelectronic integrated chips can take advantage of mature microelectronics technology, high integration density, high yield and low cost. Silicon photonics is one of the main development directions for realizing optoelectronic hybrid integration.

[0003] The main components of a general silicon photonic module include: DSP (Digital Signa l Processing, digital signal processing unit), LDD (Laser Detector Diode, laser driver), LD (Laser Diode, laser diode), MZM (Mach-Zehnder Modulator, Mach-Zehnder Modulator), TIA (Trans-Impedance Amp lif ier, transimpedance amplifier circuit) and MCU (Micro Controller Unit). MZM is a modulator used for high-speed data transmission. It can load high-speed digital signals onto optical carriers to achieve high-speed data transmission. In order for the MZM to work in the linear region, a certain voltage or current needs to be applied to it to change the crystal refractive index through the heating effect so that it can work at a reasonable working point. To determine whether the MZM is working at a reasonable working point, it is generally achieved by monitoring the photocurrent of the MPD. For a 4-way MZM, there are generally 8 MPD currents that need to be monitored. Different silicon photonic chips also have different MPD designs. One very important difference is that the MPD of some silicon photonic chips is a common anode design, while the MPD of some silicon photonic chips is a common cathode design, which will also lead to huge differences in application circuits. Utility Model Content

[0004] The purpose of the utility model is to provide a multi-channel MPD photocurrent monitoring circuit, which can solve the problem that the traditional MPD photocurrent monitoring circuit is not compatible with these two silicon photonic chips by introducing a 0 ohm resistor so that the MPDs with a common cathode and a common anode can share the same MPD photocurrent monitoring circuit. The specific technical solution is as follows:

[0005] A multi-channel MPD photocurrent monitoring circuit comprises a multi-channel MPD monitoring circuit 1, an analog switch 2, a transimpedance amplifier circuit 3 and a selective welding resistor circuit 4, wherein the analog switch 2 comprises a moving end and a fixed end, the moving end of the analog switch 2 is connected to a plurality of MPD tubes of the multi-channel MPD monitoring circuit 1, the fixed end of the analog switch 2 is connected to the selective welding resistor circuit 4, the common pole of the multi-channel MPD monitoring circuit 1 is connected to the selective welding resistor circuit 4, and the selective welding resistor circuit 4 is connected to the transimpedance amplifier circuit 3.

[0006] Furthermore, the selective welding resistance circuit 4 includes four resistance devices, and the resistance devices are sequentially connected in series to form a loop.

[0007] Furthermore, the fixed end of the analog switch 2, the ground end of the analog switch 2, the common pole of the multi-channel MPD monitoring circuit 1 and the negative input end of the transimpedance amplifier 3 are sequentially connected between two adjacent resistor devices.

[0008] Furthermore, the multi-channel MPD monitoring circuit 1 includes a common anode multi-channel MPD monitoring circuit or a common cathode multi-channel MPD monitoring circuit.

[0009] Furthermore, the common anode of the common anode multi-channel MPD monitoring circuit is connected to the selective welding resistor circuit 4 , and the common cathode of the common cathode multi-channel MPD monitoring circuit is connected to the selective welding resistor circuit 4 .

[0010] Furthermore, the fixed end of the analog switch is connected to only one of the moving ends at the same time.

[0011] Furthermore, the transimpedance amplifier circuit 3 includes an operational amplifier, a positive input terminal of the operational amplifier is connected to a power supply, and a negative input terminal of the operational amplifier is connected to the selective welding resistor circuit 4 .

[0012] Furthermore, the operational amplifier is connected to two capacitor devices and two resistor devices, one of the capacitor devices is a decoupling capacitor, and the resistor device R1 and the capacitor device C2 form an RC filter.

[0013] The utility model provides a multi-channel MPD photocurrent monitoring circuit, which has the following beneficial effects:

[0014] The utility model provides a multi-channel MPD photocurrent monitoring circuit, which introduces 0 ohm resistors so that MPDs with a common cathode and a common anode can share a set of MPD photocurrent monitoring circuits, allowing one PCB board to be compatible with two silicon photonic chips of different designs without the need to design two sets of PCBs for different silicon photonic chips, greatly reducing development costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a structural schematic diagram of a common anode multi-channel MPD photocurrent monitoring circuit in an embodiment of the utility model;

[0016] Figure 2 It is a structural schematic diagram of a common cathode multi-channel MPD photocurrent monitoring circuit in an embodiment of the utility model. DETAILED DESCRIPTION

[0017] The following will be combined with the accompanying drawings provided by the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. According to the following description, the advantages and features of the utility model will be clearer. It should be noted that the drawings are all in a very simplified form and are not in precise proportions, which are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the utility model.

[0018] In the description of the present invention, unless otherwise clearly specified and limited, the terms "connection" and "connected" should be interpreted in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integrated connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0019] In the description of the present invention, terms such as "upper", "lower", "left", "right", "front", "back", "center", "horizontal", "vertical", "top", "bottom", "inside" and "outside" and other orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of description and simplification of operation, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0020] Embodiment: The utility model provides a multi-channel MPD photocurrent monitoring circuit, which is compatible with silicon photonic chips of two types of MPDs, common cathode and common anode. This embodiment takes 8 MPDs as an example to specifically illustrate the technical solution.

[0021] See also Figure 1 and Figure 2 As shown, a common anode multi-channel MPD photocurrent monitoring circuit and a common cathode multi-channel MPD photocurrent monitoring circuit are shown, and the monitoring circuit includes a multi-channel MPD circuit 1, an analog switch 2, a transimpedance amplifier circuit 3 and a selective welding resistor circuit 4. The multi-channel MPD circuit 1 is connected to the analog switch 2, the analog switch 2 is connected to the selective welding resistor circuit 4, and the selective welding resistor circuit 4 is connected to the transimpedance amplifier circuit.

[0022] Among them, the cross-group amplifier circuit includes an operational amplifier U1 with low offset current, whose positive input terminal is connected to a fixed voltage, which can provide a reverse bias voltage to the MPD tube, and the negative input terminal is connected to the selective welding resistor circuit 4. The operational amplifier U1 is also connected to capacitors C1, C2 and resistor device R1. Capacitor device C1 is a decoupling capacitor for the power supply. Resistor device R1 and capacitor device C2 form an RC filter, which is used to limit the bandwidth to ensure wide bandwidth and low noise, and achieve a better signal-to-noise ratio. The RC value determines the –3dB cutoff frequency. Reducing R may sometimes cause ringing oscillation and instability. Increasing R will increase the sampling error. Using a lower C value will result in a higher charge kickback, but the charging time is faster. Using a higher C value can reduce the charge kickback, but the charging time will be slower. In addition, setting the RC value is the key to ensuring that a stable sample is obtained within a given sampling time. Therefore, according to past experience, R1 is 150Ω and C2 is 100nF.

[0023] The selective welding resistance circuit 4 includes four resistance devices R3, R4, R5, and R6. The resistance devices R3, R4, R5, and R6 are connected in series in sequence to form a loop. The negative input terminal of the operational amplifier U1 is connected between the resistor R3 and the resistor R6.

[0024] The analog switch 2 includes a fixed end, a ground end and multiple moving ends, wherein the fixed end is connected to the resistor R3 and the resistor R4, the ground end is connected between the resistor R4 and the resistor R5 and is grounded, and the multiple fixed ends are respectively connected to the MPD tubes of the multi-channel MPD monitoring circuit 1. The eight moving ends X0 to X7 of the analog switch 2 are controlled by the MCU, and at the same time, any moving end can be set to be connected to the fixed end X.

[0025] The multi-channel MPD circuit 1 includes two types: a common anode multi-channel MPD circuit and a common cathode multi-channel MPD circuit. The common end of the common anode multi-channel MPD circuit is the anode, and the common end of the common cathode multi-channel MPD circuit is the cathode. When the multi-channel MPD circuit is connected to the analog switch, its common end is connected between the resistor R5 and the resistor R6.

[0026] See also Figure 1 As shown in FIG. 1 , when the multi-channel MPD circuit 1 is a common anode, only the resistors R3 and R5 need to be welded, and R4 and R6 are left unwelded to form a complete MPD current detection current loop. Figure 2 As shown, when the multi-channel MPD monitoring circuit 1 is a common cathode, only the resistors R4 and R6 need to be welded, and R3 and R5 are left unwelded, so as to form a complete MPD current detection current loop.

[0027] The following example uses a common anode multi-channel MPD monitoring circuit to explain the working principle of the monitoring circuit. When MPD1 detects light, the active end X0 and the fixed end X of the analog switch are connected to form a closed loop, which will generate a photocurrent I from the cathode to the anode. The current flow direction of I is as follows: Figure 1 As shown by the arrow in the middle. According to Kirchhoff's law and Ohm's law, as well as the virtual short characteristics of the op amp, the photocurrent will generate a voltage value of (VREF+I*R2) at point A, and send this voltage to the ADC port of the MCU to generate a reporting voltage Vmon itor. For the 12-bit ADC reporting unit with a reference voltage of 2.5V, Vmon itor = 2.5*ADC (hexadecimal to decimal) / 4095, Vmon itor = VREF+I*R2, and by substituting various parameters, the photocurrent generated on the MPD can be calculated as: I = 1.136*ADC / 4095-0.0455 (mA).

[0028] In summary, the multi-channel MPD photocurrent monitoring circuit provided by the present invention can realize the compatible design of the common cathode and common anode multi-channel MPD photocurrent monitoring circuits only by selectively welding R3 / R5 or R4 / R6.

[0029] Those skilled in the art should understand that the present invention can be implemented in many other specific forms without departing from the spirit and scope of the present invention, and all other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

Claims

1. A multi-channel MPD photocurrent monitoring circuit, characterized in that: The invention comprises a multi-channel MPD monitoring circuit (1), an analog switch (2), a transimpedance amplifier circuit (3) and a selective welding resistor circuit (4); the analog switch (2) comprises a moving end and a fixed end; the moving end of the analog switch (2) is connected to a plurality of MPD tubes of the multi-channel MPD monitoring circuit (1); the fixed end of the analog switch (2) is connected to the selective welding resistor circuit (4); the common electrode of the multi-channel MPD monitoring circuit (1) is connected to the selective welding resistor circuit (4); and the selective welding resistor circuit (4) is connected to the transimpedance amplifier circuit (3).

2. The multi-channel MPD photocurrent monitoring circuit according to claim 1, characterized in that: The selective welding resistance circuit (4) comprises four resistance devices, which are sequentially connected in series to form a loop.

3. The multi-channel MPD photocurrent monitoring circuit according to claim 2, characterized in that: The fixed end of the analog switch (2), the ground end of the analog switch (2), the common pole of the multi-channel MPD monitoring circuit (1) and the negative input end of the transimpedance amplifier circuit (3) are connected in sequence between two adjacent resistor devices.

4. The multi-channel MPD photocurrent monitoring circuit according to claim 3, characterized in that: The multi-channel MPD monitoring circuit (1) comprises a common anode multi-channel MPD monitoring circuit or a common cathode multi-channel MPD monitoring circuit.

5. The multi-channel MPD photocurrent monitoring circuit according to claim 4, characterized in that: The common anode of the common anode multi-channel MPD monitoring circuit is connected to the selective welding resistance circuit (4), and the common cathode of the common cathode multi-channel MPD monitoring circuit is connected to the selective welding resistance circuit (4).

6. The multi-channel MPD photocurrent monitoring circuit according to claim 1, characterized in that: The fixed end of the analog switch is connected to only one of the moving ends at the same time.

7. The multi-channel MPD photocurrent monitoring circuit according to claim 1, characterized in that: The transimpedance amplifier circuit (3) comprises an operational amplifier, a positive input terminal of the operational amplifier is connected to a power supply, and a negative input terminal of the operational amplifier is connected to the selective welding resistor circuit (4).

8. The multi-channel MPD photocurrent monitoring circuit according to claim 7, characterized in that: The operational amplifier is connected to two capacitor devices and two resistor devices, one of the capacitor devices is a decoupling capacitor, and the resistor device R1 and the capacitor device C2 form an RC filter.

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