Driving circuit of optical thermal modulation phase shifter, optical thermal modulation phase shift control system and integrated photon system

Abstract

The invention discloses a driving circuit of an optical thermal modulation phase shifter, an optical thermal modulation phase shift control system and an integrated photon system, and belongs to the technical field of integrated photoelectronics. The driving circuit comprises an operational amplifier, a square circuit, a power tube, a first feedback resistor and a second feedback resistor. Voltage output by the power tube is divided by the first feedback resistor and the second feedback resistor to obtain divided voltage; the square voltage obtained after the divided voltage is squared by the squaring circuit is compared with the input voltage in the operational amplifier, and the square voltage is equal to the input voltage under the adjusting action of the power tube, so that the input voltage is in direct proportion to the square of the output voltage of the power tube; according to the driving circuit, a closed-loop topological structure is adopted, so that the influence caused by the process deviation of the current mode DAC is avoided. In addition, the optical thermal modulation phase shift control system comprises the drive circuit and the optical thermal modulation phase shifter, the phase shift relation from the input voltage to the optical phase shift is achieved, and the process stability is high.

Description

Technical Field

[0001] The present invention belongs to the field of integrated optoelectronic technology, and more specifically, relates to a driving circuit for an optical thermal phase shifter, an optical thermal phase shift control system, and an integrated photon system. Background Art

[0002] For an optical thermal phase shifter, the amount of phase change is proportional to the amount of temperature change. At the same time, for an optical thermal phase shifter as a resistive load, the amount of temperature change is proportional to the applied power. Therefore, there is: the phase shift amount of the optical thermal phase shifter is proportional to the electrical power applied thereto. If the resistance value of the thermal phase shifter is fixed, its phase shift amount is proportional to the square of the applied voltage. Therefore, when the voltage applied to the optical thermal phase shifter is generated by a traditional linear DAC, it will cause a resolution problem related to amplitude, and this problem will cause the phase resolution of the optical thermal phase shifter to gradually decrease as the output voltage increases. To solve this problem, it is of great significance to study a driving circuit to achieve linear driving of the optical thermal phase shifter.

[0003] Existing driving devices for optical thermal phase shifters are mostly implemented based on a driving scheme of a non-linear IDAC. It realizes a square root transfer function through an open-loop control method, and makes the output current of the driving device proportional to the square root of the input digital control signal, thereby realizing the thermal tuning drive of linear power. The digital control signal in this scheme is a digital current signal, which needs to be controlled by a current-mode DAC, and the current-mode DAC relies on the matching of active MOS transistors to work, and its monotonicity is easily affected by process deviations. As shown by the test results in a driving scheme based on a non-linear IDAC - the literature "S.Chung, H.Abediasl, and H.Hashemi, "A Monolithically Integrated Large-Scale Optical Phased Array in Silicon-on-Insulator CMOS," IEEE Journal of Solid-State Circuits, vol.53, no.1, pp.275-296, 2018", due to the problem of matching, there will be a phenomenon of partial code loss in the actual test results, thus having a greater impact on the performance of the overall scheme. Summary of the Invention

[0004] In view of the above defects or improvement requirements of the prior art, the present invention provides a driving circuit for an optical thermal phase shifter, an optical thermal phase shift control system, and an integrated photonics system, so as to solve the technical problem that the existing driving scheme based on a non-linear IDAC is vulnerable to process variations because it needs to control the output current by means of a current-mode DAC.

[0005] To achieve the above object, in a first aspect, the present invention provides a driving circuit for an optical thermal phase shifter, including: an operational amplifier, a squaring circuit, a power transistor, a first feedback resistor, and a second feedback resistor;

[0006] The first input terminal of the operational amplifier is used to connect to an external input voltage, the second input terminal is connected to one end of the squaring circuit, and the output terminal is connected to the input terminal of the power transistor; the output terminal of the power transistor serves as the output terminal of the driving circuit and is used to provide a driving voltage for the thermal phase shifter;

[0007] The output terminal of the power transistor is also grounded through the serially connected first feedback resistor and second feedback resistor, and the connection point of the first feedback resistor and the second feedback resistor is connected to the other end of the squaring circuit.

[0008] Further preferably, the above external input voltage is a digital voltage signal or an analog voltage signal; when the external input voltage is a digital voltage signal, the above driving circuit further includes a digital-to-analog conversion circuit connected before the operational amplifier.

[0009] Further preferably, the above power transistor is a metal-oxide-semiconductor type transistor.

[0010] Further preferably, the above power transistor is a bipolar transistor.

[0011] Further preferably, the above squaring circuit is a voltage squaring circuit.

[0012] Further preferably, the above squaring circuit includes: a serially connected voltage-current conversion circuit, a current squaring circuit, and a current-voltage conversion circuit.

[0013] In a second aspect, the present invention further provides an optical thermal phase shift control system, including: a driving circuit and an optical thermal phase shifter connected in series;

[0014] wherein, the driving circuit is the driving circuit provided in the first aspect of the present invention;

[0015] The phase shift amount generated by the optical thermal phase shifter is proportional to the magnitude represented by the input voltage signal of the driving circuit.

[0016] Further preferably, the optical thermal phase shifter includes: a thermal tuning resistor and a waveguide.

[0017] In a third aspect, the present invention also provides an integrated photonics system, and its adjustment unit includes the optical thermal phase modulation control system provided in the second aspect of the present invention.

[0018] Generally speaking, through the above technical solutions conceived by the present invention, the following beneficial effects can be achieved:

[0019] 1. The present invention provides a driving circuit for an optical thermal phase shifter in a first aspect, including: an operational amplifier, a squaring circuit, a power transistor, a first feedback resistor, and a second feedback resistor; the voltage output by the power transistor is divided by the first feedback resistor and the second feedback resistor to obtain a divided voltage; the squared voltage obtained by squaring the divided voltage through the squaring circuit is compared with the input voltage in the operational amplifier, and under the adjustment of the power transistor, the squared voltage is made equal to the input voltage, so that the input voltage is proportional to the square of the output voltage of the power transistor. The present invention designs a closed-loop feedback loop to achieve the square root transmission from the input voltage to the output voltage, without using a current-mode DAC, avoiding the influence caused by the process deviation of the current-mode DAC, and having higher stability.

[0020] 2. The driving circuit provided in the first aspect of the present invention forms a closed-loop feedback loop as a whole. Since there is a power transistor capable of providing a large current output in the closed-loop feedback loop, the driving ability of the voltage output can also be improved, and a large current output can be provided. Based on this, the present invention can simultaneously achieve the two functions of square root transmission from the input voltage to the output voltage and providing a large current output, without the need to first implement the square root transmission function and then improve the driving ability as in the existing circuit.

[0021] 3. The driving circuit provided in the first aspect of the present invention forms a closed-loop feedback loop as a whole. By adjusting the resistance ratio of the two resistors, the first feedback resistor and the second feedback resistor, in the closed-loop feedback loop, the continuous and stepless adjustment of the transfer function of the driving circuit can be realized, with stronger flexibility.

[0022] 4. The driving circuit provided in the first aspect of the present invention adopts a closed-loop topology structure and has higher process stability.

[0023] 5. Further, when the squaring circuit of the driving circuit provided in the first aspect of the present invention adopts a circuit including a series-connected voltage-current conversion circuit, a current squaring circuit, and a current-voltage conversion circuit, the voltage-current conversion circuit, the current squaring circuit, and the current-voltage conversion circuit can achieve a wider input and output range by adjusting the gains of the voltage-current conversion circuit and the current-voltage conversion circuit, and the working range is wider.

[0024] 6. The second aspect of the present invention provides an optical thermal phase shift control system, which uses the driving circuit provided in the first aspect of the present invention to drive an optical thermal phase shifter, such that the phase shift amount generated by the optical thermal phase shifter is proportional to the magnitude represented by the input voltage signal of the driving circuit, realizing the phase shift relationship from the input voltage to the optical phase shift, and having higher stability. Description of the Drawings

[0025] Figure 1 It is a schematic structural diagram of a driving circuit for a thermal phase shifter provided by an embodiment of the present invention;

[0026] Figure 2 It is a driving circuit provided by an embodiment of the present invention when the power transistor is a metal oxide semiconductor P-type transistor;

[0027] Figure 3 It is a schematic diagram of a current square circuit provided by an embodiment of the present invention. Detailed Embodiments

[0028] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0029] To achieve the above objective, in the first aspect, the present invention provides a driving circuit for an optical thermal phase shifter, as Figure 1 shown, including: an operational amplifier, a square circuit, a power transistor, a first feedback resistor, and a second feedback resistor;

[0030] The first input terminal of the operational amplifier is used to connect to an external input voltage, the second input terminal is connected to one end of the square circuit, and the output terminal is connected to the input terminal of the power transistor; the output terminal of the power transistor serves as the output terminal of the driving circuit and is used to provide a driving voltage for the thermal phase shifter, and can directly drive the subsequent thermal phase shifter;

[0031] The output terminal of the power transistor is also grounded through a series connection of the first feedback resistor and the second feedback resistor, and the connection point of the first feedback resistor and the second feedback resistor is connected to the other end of the square circuit, thereby forming a closed-loop feedback circuit;

[0032] In a closed-loop feedback circuit, the voltage output by the power transistor is divided by the first feedback resistor and the second feedback resistor to obtain a divided voltage; the squared voltage obtained after the divided voltage is squared by the squaring circuit is compared with the input voltage in an operational amplifier, and under the adjustment of the power transistor, the squared voltage is made equal to the input voltage, so that the input voltage is proportional to the square of the output voltage of the power transistor.

[0033] The present invention avoids the scheme of using a current DAC to control the output current. The input voltage can be generated by any DAC, which has higher flexibility.

[0034] It should be noted that the driving circuit of the existing thermal phase shifter is usually implemented by a non-linear IDAC driving scheme. Specifically, a square root transfer function is realized through an open-loop scheme, and the output current of the driving device is made proportional to the square root of the input digital control signal. The digital control signal is a digital current signal and needs to be controlled by a current-mode DAC, which is highly dependent on the current-mode DAC and is easily affected by the process deviation of the current-mode DAC. At the same time, in order to meet the driving requirements of the thermal phase shifter, after the square root transfer function is realized, the circuit also amplifies the output current through a current mirror to provide a large current output, thereby improving the driving ability, and is also affected by the process deviation of the current mirror.

[0035] To solve this technical problem, the present invention proposes a novel driving circuit for a thermal phase shifter. By designing a closed-loop feedback circuit, a square root transfer from the input voltage to the output voltage is realized, without using a current-mode DAC, avoiding the influence caused by the process deviation of the current-mode DAC, and having higher stability. At the same time, since there is a power transistor in the closed-loop feedback circuit of the present invention that can provide a large current output, the driving ability of the voltage output is also improved, and a large current output can be provided. Based on this, the present invention can simultaneously realize the two functions of square root transfer from the input voltage to the output voltage and providing a large current output, without the need to first realize the square root transfer function and then improve the driving ability as in the existing circuit.

[0036] In addition, the external input voltage in the present invention is a digital voltage signal or an analog voltage signal; when the external input voltage is a digital voltage signal, the above driving circuit further includes a digital-to-analog conversion circuit connected before the operational amplifier. The digital-to-analog conversion circuit is a voltage-mode DAC. It should be noted that the voltage-mode DAC relies on the matching of passive resistors or capacitors and is less affected by process deviations, so the stability is also relatively high.

[0037] It should be noted that the operational amplifier can be any differential input single-ended output type operational amplifier.

[0038] In an alternative embodiment, the above power transistor is a metal-oxide-semiconductor transistor, which may be a metal-oxide-semiconductor P-type transistor or a metal-oxide-semiconductor N-type transistor; specifically, as Figure 2 shown is the drive circuit when the power transistor is a metal-oxide-semiconductor P-type transistor. In another alternative embodiment, the above power transistor is a bipolar transistor, which may be a PNP-type bipolar transistor or an NPN-type bipolar transistor.

[0039] In an alternative embodiment, the above squaring circuit is a voltage squaring circuit, which directly squares the divided voltage. In another alternative embodiment, the above squaring circuit includes: a series-connected voltage-current conversion circuit, a current squaring circuit, and a current-voltage conversion circuit.

[0040] It should be noted that, compared with the voltage squaring circuit which can only have a fixed input and output range, the squaring circuit including the voltage-current conversion circuit, the current squaring circuit, and the current-voltage conversion circuit can achieve a wider input and output range by adjusting the gains of the voltage-current conversion circuit and the current-voltage conversion circuit, and has a wider working range.

[0041] It should be noted that there are various current squaring circuits, such as Figure 3 shown is a schematic diagram of one of the current squaring circuits.

[0042] Denote the bias currents of MOS transistors M1 and M2 as I0. When there is an input current I in , the currents flowing through M1, M2, and M3 are I1, I2, and I3 respectively, then there is:

[0043] I3 - I1 = K(V X - 2V th )(V X - V Y )

[0044]

[0045] Subtracting the fixed term 2I0 from I out can obtain the square relationship between the input and the output.

[0046] In a second aspect, the present invention further provides an optical thermal phase shift control system, including: a series-connected drive circuit and a thermal phase shifter;

[0047] wherein, the drive circuit is the drive circuit provided in the first aspect of the present invention. The phase shift amount generated by the optical thermal phase shifter is proportional to the magnitude represented by the input voltage signal of the drive circuit.

[0048] It should be noted that the input of the optical thermal phase shift control system can be a digital signal or an analog signal, and the generated phase shift amount is proportional to the magnitude represented by the input signal.

[0049] The related technical solutions are the same as the driving circuit provided in the first aspect of the present invention, and will not be elaborated here.

[0050] In an optional implementation manner, the optical thermal phase shifter includes: a thermal tuning resistor and a waveguide, and the introduced optical phase shift amount is proportional to the electrical power applied to the thermal phase shifter.

[0051] It should be noted that the thermal tuning resistor can be placed above, below or next to the waveguide, and there are many spatial structures, but they are all composed of a thermal tuning resistor and a waveguide close to the thermal tuning resistor, which is not limited here.

[0052] The present invention designs an optical thermal phase shift control system, which realizes the phase shift relationship from the input voltage to the optical phase shift. Compared with the existing control schemes, its driving circuit adopts a closed-loop topology structure and has higher process stability.

[0053] In a third aspect, the present invention also provides an integrated photonics system, and its adjustment unit includes the optical thermal phase shift control system provided in the second aspect of the present invention.

[0054] The related technical solutions are the same as the optical thermal phase shift control system provided in the second aspect of the present invention, and will not be elaborated here.

[0055] It should be noted that the integrated photonics system includes but is not limited to optical modulators, filters, lasers, photodiodes, optical switches, optical waveguides, optoelectronic oscillators, active polarization controllers or optical frequency combs.

[0056] Those skilled in the art can easily understand that the above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A driving circuit for an optical thermal phase shifter, characterized in that Comprising: An operational amplifier, a squaring circuit, a power transistor, a first feedback resistor, and a second feedback resistor; The first input terminal of the operational amplifier is used to connect to an external input voltage, the second input terminal is connected to one end of the squaring circuit, and the output terminal is connected to the input terminal of the power transistor; the output terminal of the power transistor serves as the output terminal of the drive circuit and is used to provide a drive voltage for the thermal phase shifter; The output terminal of the power transistor is also grounded through the series-connected first feedback resistor and the second feedback resistor, and the connection point of the first feedback resistor and the second feedback resistor is connected to the other end of the squaring circuit.

2. The drive circuit according to claim 1, wherein The external input voltage is a digital voltage signal or an analog voltage signal; when the external input voltage is a digital voltage signal, the drive circuit further includes a digital-to-analog conversion circuit connected before the operational amplifier.

3. The drive circuit according to claim 1, characterized in that, The power transistor is a metal-oxide-semiconductor type transistor.

4. The drive circuit according to claim 1, characterized in that, The power transistor is a bipolar transistor.

5. The drive circuit according to any one of claims 1-4, characterized in that, The squaring circuit is a voltage squaring circuit.

6. The drive circuit according to any one of claims 1-4, characterized in that, The squaring circuit includes: a series-connected voltage-current conversion circuit, a current squaring circuit, and a current-voltage conversion circuit.

7. An optical thermal phase modulation control system, characterized in that, Comprising: A series-connected drive circuit and an optical thermal phase shifter; Wherein, the drive circuit is the drive circuit according to any one of claims 1-6.

8. The optical thermal phase modulation control system according to claim 7, characterized in that The optical thermal phase shifter includes: a thermal tuning resistor and a waveguide.

9. An integrated photonics system, characterized in that, Its adjustment unit includes: the optical thermal phase shift control system according to any one of claims 7-8.

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