Detection device and detection method

Abstract

A detection device is suitable for an MZ modulator and a photoelectric detector which perform bias point control based on a disturbance signal. The detection device comprises a current-voltage conversion and gain unit, a capacitor, a filtering unit, a direct-current voltage clamping unit, an analog-to-digital converter and a microcontroller. The detection device executes a detection method so as to convert and amplify a current signal measured by the photoelectric detector through the current-voltage conversion and gain unit to generate an adjusted voltage signal. DC component isolation, filtering and DC component clamping are respectively carried out through the capacitor, the filtering unit and the DC voltage clamping unit, sampling is carried out through the analog-to-digital converter, a digital signal obtained through sampling is received through the microcontroller, algorithm processing can be carried out on the digital signal, and the processed digital signal is processed through the DC voltage clamping unit. And the working point of the MZ modulator is dynamically controlled in real time.

Description

Technical Field

[0001] The present invention relates to a detection device and a detection method, in particular to a detection device and a detection method for an MZ modulator controlled by a perturbation signal as a bias point. Background Art

[0002] The MZ electro-optic modulator is a modulation device widely used in modern optical fiber communication systems. In order to maintain stable control of the bias voltage (i.e., the operating point) of the MZ modulator when the environment (such as temperature) changes, one known technique is a control method based on a perturbation signal. That is, a perturbation signal (i.e., an AC small signal) with a predetermined frequency is superimposed on the DC bias voltage, and the output light source of the MZ modulator will first pass through a splitter, so that, for example, 99% of the light beam is used for the transmission of the optical signal, and 1% of the light beam is input to a photodetector (PD). Then, the conventional method will receive the current signal of the photodetector through a transimpedance amplifier (TIA) circuit to convert it into a voltage signal, and then sample the voltage signal through an analog-to-digital converter (ADC), and filter and calculate the sampled digital signal in a software calculation manner through a microcontroller to obtain the change of the perturbation signal. However, the above-mentioned conventional method has a slow processing speed due to the need for a large amount of operations by the microcontroller, which in turn affects and limits the accuracy and speed that the MZ modulator can control, and cannot immediately reflect the change of the operating point of the MZ modulator caused by the environmental change and make an immediate tracking adjustment. Therefore, whether there are other detection devices and detection methods for MZ modulators and photodetectors based on perturbation signals as bias points has become a problem to be solved. Summary of the Invention

[0003] The object of the present invention is to provide a detection device and a detection method with high precision and high speed.

[0004] Thus, in one aspect of the present invention, there is provided a detection device suitable for an MZ modulator and a photodetector (PD) controlled by a perturbation signal as a bias point, and includes a current-voltage conversion and gain unit, a capacitor, a filtering unit, a DC voltage clamping unit, an analog-to-digital converter, and a microcontroller.

[0005] The current-voltage conversion and gain unit is electrically connected to the photodetector, and is used to convert the current signal measured by the photodetector into a voltage signal, and adjust the amplitude of the voltage signal according to the adjustment of the resistance value of the variable resistor to generate an adjusted voltage signal.

[0006] The capacitor is electrically connected to the current-voltage conversion and gain unit, and includes a first terminal and a second terminal for receiving the adjustment voltage signal. The filtering unit is electrically connected to the second terminal of the capacitor to filter out a filtered voltage signal corresponding to the frequency band of the disturbance signal.

[0007] The DC voltage clamping unit is electrically connected to the filtering unit and clamps the DC component of the filtered voltage signal at the middle value of the dynamic range. The analog-to-digital converter (ADC) is electrically connected to the DC voltage clamping unit, has an input specification within the dynamic range, and receives the filtered voltage signal for sampling to generate a digital signal.

[0008] The microcontroller is electrically connected to the current-voltage conversion and gain unit to control the resistance value of the variable resistor, and is electrically connected to the analog-to-digital converter to receive the digital signal.

[0009] In some embodiments, the detection device further includes a gain adjustment unit, which is electrically connected to the filtering unit, the microcontroller, and the DC voltage clamping unit, receives the filtered voltage signal from the filtering unit, receives an amplification gain control signal from the microcontroller, and amplifies the filtered voltage signal according to the amplification gain control signal by an amplification gain value corresponding to the amplification gain control signal, and transmits the amplified filtered voltage signal to the DC voltage clamping unit. The microcontroller determines the amplification gain control signal and the amplification gain value according to the amplified filtered voltage signal.

[0010] In some embodiments, when the photodetector is of the output photocurrent type, the current-voltage conversion and gain unit is the variable resistor for receiving the current signal from the photodetector. When the photodetector is of the input photocurrent type, the current-voltage conversion and gain unit is a current-voltage conversion circuit for outputting the current signal to the photodetector. The current-voltage conversion circuit includes the variable resistor. The microcontroller determines the resistance value of the variable resistor according to the amplified filtered voltage signal.

[0011] In some embodiments, the variable resistor includes a first resistor, a second resistor, and a switch unit. The resistance value of the first resistor is greater than that of the second resistor. The microcontroller controls the switch unit to control the current signal to flow through the first resistor or the second resistor to correspondingly change the resistance value.

[0012] In some other embodiments, the variable resistor is a variable gain resistor chip. The microcontroller changes the resistance value by transmitting a resistance value control signal to the variable gain resistor chip.

[0013] Thus, a concept of the present invention provides a detection method applicable to an MZ modulator, a photodetector, a current-voltage conversion and gain unit, a capacitor, a filtering unit, a DC voltage clamping unit, an analog-to-digital converter with an input specification having a dynamic range, and a microcontroller that perform bias point control based on a perturbation signal. The detection method includes steps (A) to (F).

[0014] In step (A), the current signal measured by the photodetector is converted into a voltage signal by the current-voltage conversion and gain unit, and the voltage signal is amplitude-adjusted according to the adjustment of the resistance value of the variable resistor to generate an adjusted voltage signal.

[0015] In step (B), the DC component of the adjusted voltage signal is isolated by the capacitor to generate the adjusted voltage signal after isolating the DC component.

[0016] In step (C), the adjusted voltage signal is filtered by the filtering unit to generate a filtered voltage signal corresponding to the frequency band of the perturbation signal.

[0017] In step (D), the DC component of the filtered voltage signal is clamped at the intermediate value of the dynamic range by the DC voltage clamping unit.

[0018] In step (E), the filtered voltage signal is received by the analog-to-digital converter for sampling to generate a digital signal.

[0019] In step (F), the microcontroller controls the resistance value of the variable resistor and receives the digital signal.

[0020] In some embodiments, the detection method is also applicable to a gain adjustment unit, and further includes, between steps (C) and (D), (G) amplifying the filtered voltage signal by the gain adjustment unit according to an amplification gain control signal from the microcontroller by an amplification gain value corresponding to the amplification gain control signal, and transmitting the amplified filtered voltage signal to the DC voltage clamping unit. The microcontroller determines the amplification gain control signal and the amplification gain value according to the amplified filtered voltage signal.

[0021] In some embodiments, in step (A), when the photodetector is of the output photocurrent type, the current-voltage conversion and gain unit is the variable resistor to receive the current signal from the photodetector. When the photodetector is of the input photocurrent type, the current-voltage conversion and gain unit is a current-voltage conversion circuit to output the current signal to the photodetector. The current-voltage conversion circuit includes the variable resistor. The microcontroller determines the resistance value of the variable resistor according to the amplified filtered voltage signal.

[0022] In some embodiments, in step (A), the variable resistor includes a first resistor, a second resistor, and a switch unit. The resistance value of the first resistor is greater than that of the second resistor. The microcontroller controls the switch unit to control the current signal to flow through the first resistor or the second resistor to correspondingly change the resistance value.

[0023] In other embodiments, in step (A), the variable resistor is a variable gain resistor chip. The microcontroller changes the resistance value by transmitting a resistance value control signal to the variable gain resistor chip.

[0024] The beneficial effects of the present invention are as follows: Through the current-voltage conversion and gain unit, the capacitor, the filtering unit, and the DC voltage clamping unit, current-voltage conversion and amplification, isolation of DC components, filtering, and clamping of DC components are respectively performed, and then a digital signal is generated by sampling through the analog-to-digital converter, and the microcontroller receives the digital signal. Furthermore, it is possible to implement a detection device and a detection method that first perform conversion and amplification, isolation of DC components, filtering, and clamping of DC components in a hardware manner, and then obtain the digital signal corresponding to the disturbance signal in a software manner after analog-to-digital conversion, and have high precision and high speed. Description of the Drawings

[0025] Figure 1 is a block diagram illustrating an embodiment of the detection device of the present invention;

[0026] Figure 2 is a circuit schematic diagram illustrating one aspect of a photodetector in this embodiment;

[0027] Figure 3 is a circuit schematic diagram illustrating another aspect of a photodetector in this embodiment;

[0028] Figure 4 is a circuit schematic diagram illustrating one aspect of a gain adjustment unit in this embodiment;

[0029] Figure 5 is a circuit schematic diagram showing an aspect of a DC voltage clamping unit of this embodiment; and

[0030] Figure 6 is a flowchart showing an embodiment of the detection method of the present invention. Detailed implementation manners

[0031] The present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0032] Before the present invention is described in detail, it should be noted that in the following description, similar elements are denoted by the same reference numerals.

[0033] Refer to Figure 1 , an embodiment of the detection device of the present invention is applicable to an MZ modulator 93, a laser light source 91, a signal generator 92, a beam splitter 94, an optical fiber 95, and a photodetector 96. The MZ modulator 93 (i.e., an MZ electro-optic modulator) receives the laser from the laser light source 91 and includes a radio frequency (RF) pin and a DC bias pin. The RF pin receives the signal from the signal generator 92. The DC bias pin receives a DC bias voltage and a (AC) perturbation signal superposed from a microcontroller. It should be specifically noted that: the control device for controlling the bias point based on the perturbation signal belongs to a prior art and is not the part to be improved by the present invention, so Figure 1 is not shown in it either. The output light source of the MZ modulator 93 will first pass through the beam splitter 94, so that, for example, 99% of the light beam is used for the optical signal transmission of the optical fiber 95, and 1% of the light beam is input to the photodetector 96.

[0034] The detection device includes a current-voltage conversion and gain unit 1, a capacitor 2, a filtering unit 3, a gain adjustment unit 4, a DC voltage clamping unit 5, an analog-to-digital converter 6, and a microcontroller 7.

[0035] The current-voltage conversion and gain unit 1 is electrically connected to the photodetector 96 and is used to convert a current signal measured by the photodetector 96 into a voltage signal and amplify the voltage signal according to a resistance value of a variable resistor to generate an adjusted voltage signal. That is, by adjusting the resistance value of the variable resistor, the gain is adjusted to generate the adjusted voltage signal with an adjusted amplitude.

[0036] Refer to Figure 1 and Figure 2 , when the photodetector 96 is of an output photocurrent type (such as Figure 2When the current signal flows out from an output terminal 961 of the photodetector 96 as shown, the current-voltage conversion and gain unit 1 is the variable resistor to receive the current signal, and generate the adjustment voltage signal across the two ends of the variable resistor, that is, achieving the functions of voltage conversion and signal amplification simultaneously.

[0037] Refer to Figure 1 and Figure 3 , when the photodetector 96 belongs to an input photo-generated current type (such as Figure 3 shown), the current signal flows into the output terminal 961 of the photodetector 96, then the current-voltage conversion and gain unit 1 is a current-voltage conversion (TIA) circuit to output the current signal to the photodetector 96. The current-voltage conversion circuit includes an operational amplifier, multiple resistors, and the variable resistor, and also outputs the adjustment voltage signal.

[0038] In this embodiment, the variable resistor is a variable gain resistor chip, for example, the model is TPL0102-100RUCR, but not limited thereto. The variable gain resistor chip receives a resistance value control signal from the microcontroller 7 to change the resistance value.

[0039] In other embodiments, the variable resistor can also be changed to include a first resistor, a second resistor, and a switch unit. The switch unit includes a first switch connected in series with the first resistor, and a second switch connected in series with the second resistor. The series-connected first resistor and the first switch, and the series-connected second resistor and the second switch are in parallel. The resistance value of the first resistor is greater than that of the second resistor. The first switch and the second switch respectively receive multiple control signals included in the resistance value control signal from the microcontroller 7 to control the conduction or non-conduction of the first switch or the second switch, thereby controlling the current signal to flow through the first resistor or the second resistor to correspondingly change the resistance value.

[0040] The capacitor 2 is electrically connected to the current-voltage conversion and gain unit 1 and the filtering unit 3, and includes a first end for receiving the adjustment voltage signal from the current-voltage conversion and gain unit 1 and a second end electrically connected to the filtering unit 3, and is used to isolate the DC component of the signal. For example, the capacitance value of the capacitor 2 is 1uF.

[0041] The filtering unit 3 receives the adjustment voltage signal from the capacitor 2 after isolating the DC component, and is used to filter out a filtered voltage signal corresponding to a frequency band of the perturbation signal. For example, the frequency band is between 1 to 2 kHz, and the filtering unit 3 is, for example, a second-order band-pass filtering circuit, or a first-order low-pass filtering circuit and a first-order high-pass filtering circuit.

[0042] The gain adjustment unit 4 is electrically connected to the filtering unit 3, the microcontroller 7, and the DC voltage clamping unit 5, receives the filtered voltage signal from the filtering unit 3, receives an amplification gain control signal from the microcontroller 7, and according to the amplification gain control signal, amplifies the filtered voltage signal by an amplification gain value corresponding to the amplification gain control signal, and transmits the amplified filtered voltage signal to the DC voltage clamping unit 5.

[0043] Refer to Figure 1 and Figure 4 , Figure 4 Exemplarily, it is described that the gain adjustment unit 4 is a current-voltage conversion circuit, and the architecture of this current-voltage conversion circuit can also be used for the current-voltage conversion and gain unit 1. The current-voltage conversion circuit includes an input terminal 47 for receiving the filtered voltage signal from the filtering unit 3, an output terminal 48 for outputting the amplified filtered voltage signal, an operational amplifier 41, a plurality of resistors 42-45, and a capacitor 46. The model of the operational amplifier is, for example, AD8034ART-EBZ, but not limited thereto. The resistance values of the resistors 42-44 are, for example, all 10 kΩ. The resistor 45 is the variable resistor as described above and is controlled by the amplification gain control signal from the microcontroller 7 to change the resistance value, thereby changing the gain. The capacitance value of the capacitor 46 is, for example, 10 pF and is used to increase the loop stability of the negative feedback amplifier circuit to prevent the operational amplifier 41 from oscillating.

[0044] Refer to Figure 1 , Figure 4 , and Figure 5 , the DC voltage clamping unit 5 is used to clamp the DC component of the filtered voltage signal from the gain adjustment unit 4 at an intermediate value within a dynamic range. The dynamic range is the input specification of the analog-to-digital converter 6 and is, for example, 2.5 volts. Figure 5 Exemplarily, a state of the DC voltage clamping unit 5 is described, and it includes an input terminal 53 electrically connected to the output terminal 48, an output terminal 54 electrically connected to the analog-to-digital converter 6, and two resistors 51, 52. The resistance values of the two resistors 51, 52 are, for example, 10 kΩ. Since the dynamic range is 2.5 volts, the intermediate value is 1.25 volts. Through the electrical connection relationship of the two resistors 51, 52 with the 2.5-volt power supply and the ground terminal, the DC component of the filtered voltage signal is clamped at 1.25 volts.

[0045] The analog-to-digital converter 6, for example, has a digital output of sixteen bits, and the input specification of the dynamic range is 2.5 volts, and is used to receive the filtered voltage signal after being clamped, and sample it to generate a digital signal.

[0046] The microcontroller 7 is also electrically connected to the analog-to-digital converter 6 to receive and obtain the digital signal corresponding to the disturbance signal, and is also electrically connected to the current-voltage conversion and gain unit 1 to output the resistance value control signal to control the resistance value of the variable resistor. More specifically, the output terminal 48 of the gain adjustment unit 4 also outputs the amplified filtered voltage signal to the microcontroller 7. The microcontroller 7 includes a built-in analog-to-digital converter to sample the amplified filtered voltage signal to obtain the amplitude of the signal, so that the microcontroller 7 can select the resistance value of the variable resistor and the amplification gain according to the amplitude of the amplified filtered voltage signal according to the pre-set plan, so as to determine the corresponding resistance value control signal and the amplification gain control signal, and further make the amplified filtered voltage signal reach the signal amplification as much as possible without distortion.

[0047] See Figure 1 And Figure 6 , the detection method of the present invention is applicable to the MZ modulator 93, the photodetector 96, and the detection device based on the disturbance signal for bias point control, and includes steps S1 to S7.

[0048] In step S1, the current-voltage conversion and gain unit 1 converts the current signal measured by the photodetector 96 into a voltage signal, and amplifies the voltage signal according to the resistance value of the variable resistor to generate the adjusted voltage signal.

[0049] In step S2, the capacitor 2 isolates the DC component from the adjusted voltage signal to generate the adjusted voltage signal after isolating the DC component.

[0050] In step S3, the filtering unit 3 filters the adjusted voltage signal to generate the filtered voltage signal corresponding to the frequency band of the disturbance signal.

[0051] In step S4, the gain adjustment unit 4 amplifies the filtered voltage signal by the amplification gain value corresponding to the amplification gain control signal according to the amplification gain control signal from the microcontroller 7, and transmits the amplified filtered voltage signal to the DC voltage clamping unit 5. The microcontroller 7 determines the amplification gain control signal and the amplification gain value according to the amplified filtered voltage signal.

[0052] In step S5, the DC component of the filtered voltage signal is clamped at the intermediate value of the dynamic range by the DC voltage clamping unit 5.

[0053] In step S6, the filtered voltage signal is received by the analog-to-digital converter 6 to sample and generate the digital signal.

[0054] In step S7, the microcontroller 7 controls the resistance value of the variable resistor and receives the digital signal.

[0055] It should be particularly noted that: in other embodiments, the gain adjustment unit 4 and step S4 can also be omitted.

[0056] In summary, through the current-voltage conversion and gain unit 1, the capacitor 2, the filtering unit 3, and the DC voltage clamping unit 5, current-voltage conversion and amplification, isolation of DC components, filtering, and clamping of DC components are respectively performed. Then, the analog-to-digital converter 6 samples to generate the digital signal, and the microcontroller 7 receives the digital signal. Furthermore, it is possible to implement a detection device and a detection method that first perform conversion and amplification, isolation of DC components, filtering, and clamping of DC components in a hardware manner, and then obtain the digital signal corresponding to the disturbance signal in a software manner after analog-to-digital conversion, and have high precision and high speed. Therefore, the object of the present invention can indeed be achieved.

[0057] However, the above are only embodiments of the present invention, and the scope of implementation of the present invention cannot be limited thereby. That is, all simple equivalent changes and modifications made according to the content of the claims of the present invention and the patent specification still fall within the scope covered by the patent of the present invention.

Claims

1. A detection device, applicable to an MZ modulator and a photodetector (PD) that perform bias point control based on a disturbance signal, characterized in that: the detection device includes: a current-voltage conversion and gain unit, electrically connected to the photodetector, and configured to convert the current signal measured by the photodetector into a voltage signal, and adjust the amplitude of the voltage signal according to the adjustment of the resistance value of a variable resistor to generate an adjusted voltage signal; a capacitor, electrically connected to the current-voltage conversion and gain unit, and including a first terminal and a second terminal for receiving the adjusted voltage signal; a filtering unit, electrically connected to the second terminal of the capacitor, to filter out a filtered voltage signal corresponding to the frequency band of the disturbance signal; a DC voltage clamping unit, electrically connected to the filtering unit, and clamping the DC component of the filtered voltage signal at the middle value of the dynamic range; an analog-to-digital converter (ADC), electrically connected to the DC voltage clamping unit, having an input specification within the dynamic range, and receiving the filtered voltage signal for sampling to generate a digital signal; and a microcontroller, electrically connected to the current-voltage conversion and gain unit to control the resistance value of the variable resistor, and electrically connected to the analog-to-digital converter to receive the digital signal.

2. The detection device according to claim 1, characterized in that: the detection device further includes a gain adjustment unit, electrically connected to the filtering unit, the microcontroller, and the DC voltage clamping unit, receiving the filtered voltage signal from the filtering unit, and receiving an amplification gain control signal from the microcontroller, and according to the amplification gain control signal, amplifying the filtered voltage signal by an amplification gain value corresponding to the amplification gain control signal, and transmitting the amplified filtered voltage signal to the DC voltage clamping unit, and the microcontroller determines the amplification gain control signal and the amplification gain value according to the amplified filtered voltage signal.

3. The detection device according to claim 2, characterized in that: when the photodetector is of the output photocurrent type, the current-voltage conversion and gain unit is the variable resistor to receive the current signal from the photodetector; when the photodetector is of the input photocurrent type, the current-voltage conversion and gain unit is a current-voltage conversion circuit to output the current signal to the photodetector, the current-voltage conversion circuit includes the variable resistor, and the microcontroller determines the resistance value of the variable resistor according to the amplified filtered voltage signal.

4. The detection device according to claim 3, characterized in that: the variable resistor includes a first resistor, a second resistor, and a switch unit, the resistance value of the first resistor is greater than that of the second resistor, and the microcontroller controls the switch unit to control the current signal to flow through the first resistor or the second resistor to correspondingly change the resistance value.

5. The detection device according to claim 3, characterized in that: The variable resistor is a variable gain resistor chip, and the microcontroller changes the resistance value by transmitting a resistance value control signal to the variable gain resistor chip.

6. A detection method applicable to an MZ modulator, a photodetector, a current-voltage conversion and gain unit, a capacitor, a filtering unit, a DC voltage clamping unit, an analog-to-digital converter with an input specification having a dynamic range, and a microcontroller that perform bias point control based on a disturbance signal, characterized in that: the detection method includes: (A) converting the current signal measured by the photodetector into a voltage signal through a current-voltage conversion and gain unit, and adjusting the amplitude of the voltage signal according to the adjustment of the resistance value of the variable resistor to generate an adjusted voltage signal; (B) isolating the DC component of the adjusted voltage signal through a capacitor to generate the adjusted voltage signal after isolating the DC component; (C) filtering the adjusted voltage signal through a filtering unit to generate a filtered voltage signal corresponding to the frequency band of the disturbance signal; (D) clamping the DC component of the filtered voltage signal at the intermediate value of the dynamic range through a DC voltage clamping unit; (E) receiving the filtered voltage signal through the analog-to-digital converter to sample and generate a digital signal; and (F) controlling the resistance value of the variable resistor through the microcontroller and receiving the digital signal.

7. The detection method according to claim 6 is also applicable to a gain adjustment unit, characterized in that: the detection method further includes (G) between steps (C) and (D), amplifying the filtered voltage signal by a gain value corresponding to the amplification gain control signal through the gain adjustment unit according to the amplification gain control signal from the microcontroller, and transmitting the amplified filtered voltage signal to the DC voltage clamping unit, and the microcontroller determines the amplification gain control signal and the amplification gain value according to the amplified filtered voltage signal.

8. The detection method of the information according to claim 7, characterized in that: in step (A), when the photodetector is of the output photocurrent type, the current-voltage conversion and gain unit is the variable resistor to receive the current signal from the photodetector, and when the photodetector is of the input photocurrent type, the current-voltage conversion and gain unit is a current-voltage conversion circuit to output the current signal to the photodetector, the current-voltage conversion circuit includes the variable resistor, and the microcontroller determines the resistance value of the variable resistor according to the amplified filtered voltage signal.

9. The detection method of the information according to claim 8, characterized in that: in step (A), the variable resistor includes a first resistor, a second resistor, and a switch unit, the resistance value of the first resistor is greater than the resistance value of the second resistor, and the microcontroller controls the switch unit to control the current signal to flow through the first resistor or the second resistor to correspondingly change the resistance value.

10. The detection method of information according to claim 8, characterized in that: in step (A), the variable resistor is a variable gain resistor chip, and the microcontroller changes the resistance value by transmitting a resistance value control signal to the variable gain resistor chip.

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