WO2015161538A1

WO2015161538A1 - Device for stabilizing spectrum of micro-ring resonator

Info

Publication number: WO2015161538A1
Application number: PCT/CN2014/077742
Authority: WO
Inventors: 廖明乐; 邱昆; 武保剑; 王利辉; 张中一
Original assignee: 电子科技大学
Priority date: 2014-04-24
Filing date: 2014-05-18
Publication date: 2015-10-29
Also published as: CN103955247B; CN103955247A

Abstract

A device for stabilizing a spectrum of a micro-ring resonator (1), comprising a micro-ring resonator (1), a signal processing unit (2), an FPGA control unit (3), a source meter functional module (4) and a heater drive unit (5), wherein after a current is input into a PIN junction of the micro-ring resonator (1), the amount of variation of a voltage at two ends of the PIN junction of the micro-ring resonator (1) caused by temperature variation is detected, and then after the amount of variation of the voltage is processed through the signal processing unit (2) and the FPGA control unit (3), a voltage drive signal for stabilizing a spectrum of the micro-ring resonator (1) is generated. In the actual configuration, the PIN junction detects the working temperature of each micro-ring switch in real time, so that the problem that a large number of micro-rings cannot be positioned is solved, moreover, no additional functional devices are needed, while the device has the advantages of having high temperature detection speed, being low in cost and being simple in design process and easy to operate, and the device can meet the requirements of high speed development of current optical communication systems.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the field of optical communication technology, and more particularly to an apparatus for stabilizing the spectrum of a microring resonator.

Background technique

With the development of optical communication systems in the direction of high speed, high capacity, low loss, and low cost, higher and higher requirements are imposed on optical devices. In recent years, with the improvement of optical waveguide technology, photonic integration technology has received much attention. Microring resonators have high quality factor (Q value), compact structure, high integration, compatibility with existing CMOS processes, etc., and have broad application prospects in optical communication networks.

In silicon-based materials, the main physical effects are carrier dispersion effects, thermo-optical effects, and the like. The carrier dispersion effect refers to the fact that the injection or extraction of carriers causes changes in the free carriers in the optical waveguide to cause changes in the refractive index, and has the advantages of high speed, polarization insensitivity, large refractive index change, etc., which can be in the microring. High-speed switching or modulation is achieved using the carrier dispersion effect. The thermo-optic effect is to change the refractive index of the micro-ring by changing the refractive index of the optical waveguide as a function of temperature. The processing precision of the existing CMOS process is difficult to achieve a perfect match with the ideal design, and the thermo-optic effect can be used to compensate for the resonance wavelength drift caused by the process error. However, the microring resonator is extremely sensitive to temperature, and its switching spectrum is susceptible to the temperature of the chip, which degrades the performance of the microring optical switch. In order to stabilize the switching spectrum of the microring resonator, not only a high-precision adjustment circuit but also a timely and effective control of the micro-ring operating temperature is required.

In the prior art, since the size of the micro/nano optics is small, only on the order of micrometers, it is a major difficulty to monitor the temperature within such a small scale. The composite optical integrated device developed in recent years can realize the optical device with stable temperature property by using the special material characteristics which are not sensitive to temperature, but the processing technology of the composite material cannot be compatible with the CMOS process, and the cost is high. Therefore, in the silicon-based material, in order to achieve precise control of the operating temperature of the microring resonator, a metal film is coated on the micro-ring device for heating, although the existing processing technology has been able to connect the micro-heater and the PIN junction. It is fabricated in a microring resonator chip, but it cannot integrate a temperature sensor in the microring chip, detects the operating temperature of the microring chip, and stabilizes the spectrum of the microring resonator by the amount of temperature change. Summary of the invention The object of the present invention is to overcome the deficiencies of the prior art and provide a device for stabilizing the spectrum of a microring resonator, which stabilizes the microring by detecting the amount of change in the voltage across the PIN junction of the microring resonator due to temperature changes of the microring resonator. The spectrum of the resonator has the characteristics of simple design process and low cost.

In order to achieve the above object, the present invention provides an apparatus for stabilizing the spectrum of a microring resonator, which is characterized by comprising:

A microring resonator, including a heater and a PIN junction, is enabled to open or close the microring resonator by loading a current on the PIN junction through the source meter function module, and simultaneously detecting a temperature change of the microring resonator;

A signal processing unit includes an amplification, shaping, filtering circuit and a high-precision analog/digital converter (AD) for sequentially applying a voltage variation ΔΙΙ fed back from the source table function module to the high-order, amplified, and filtered processing input to the high An accurate analog/digital converter (AD) that converts the analog signal into a digital signal and feeds it back to the FPGA control unit;

An FPGA control unit is configured to generate a switch driving signal of the a channel, receive the digital signal from the signal processing unit at the same time, and fit and analyze the output voltage signal of the b channel by fitting the digital signal; the switch driving signal of the a channel is input to The source meter function module, the voltage driving signal of the b channel is input to the heater driving unit module;

A source meter function module, including a current type digital/analog converter (DA) and a voltage follower; the source meter function module receives a switch signal of the a channel, converts it into a constant current i through a high precision DA, and then constants The current i is input to the right half arm PIN junction of the microring resonator; at the same time, the change AU of the voltage across the PIN junction of the microring resonator due to the temperature change is detected, and the voltage variation ΔΙΙ is fed back to the signal processing unit. ;

a heater driving unit, comprising a DA and a peripheral matching circuit; after receiving the voltage driving signal of the b channel, the heater driving unit first converts the analog voltage driving signal by the high precision DA, and then passes the analog voltage driving signal to the peripheral matching circuit. After the impedance matching is performed, the heater is loaded into the microring resonator, and the temperature of the microring resonator is changed by changing the voltage applied to the heater. The device control unit outputs _a channel switch driving signal to the source after the device is started. The table function module generates a constant current i after the DA conversion in the source table function module, and then inputs the constant current i to the right half arm PIN junction of the microring resonator to control the opening or closing of the microring resonator; the PIN junction is input. After the current, the temperature variation of the microring resonator can be detected, and the variation ΔΙΙ of the voltage across the PIN junction of the microring resonator caused by the temperature change is obtained, and the voltage variation ΔΙΙ is amplified, shaped, filtered, and AD by the signal processing unit. At After obtaining the digital signal, the digital signal is input to the FPGA control unit. After fitting and analyzing, the voltage driving signal of the output b channel is loaded into the heater driving unit module, and the voltage driving signal of the b channel is converted by the DA of the heater driving unit. After generating an analog voltage driving signal, the heater is loaded into the microring resonator after impedance matching with the peripheral matching circuit of the heater driving unit, and the temperature of the microring resonator is adjusted by changing the voltage applied to the heater to change the temperature of the microring resonator. Thereby maintaining the spectral stability of the microring resonator.

Further, the switch driving signal of the a channel is input to the source table function module before the FPGA control unit analyzes the digital signal.

The object of the invention is achieved in this way:

The device for stabilizing the spectrum of the microring resonator, after the current is applied to the PIN junction of the microring resonator, detects the change of the voltage across the PIN junction of the microring resonator due to the temperature change of the microring resonator, and then After the voltage variation is processed by the signal processing unit and the FPGA control unit, a voltage driving signal for stabilizing the spectrum of the microring resonator is generated, which has the characteristics of simple design process and easy operation. In the actual configuration, the PIN junction detects the operating temperature of each micro-ring switch in real time, solves the problem that the number of micro-rings cannot be located, and does not require additional functional devices, and has a fast temperature detection and low cost. The advantage is that it can adapt to the needs of the rapid development of current optical communication systems.

At the same time, the device for stabilizing the spectrum of the microring resonator of the present invention has the following beneficial effects:

(1) The invention stabilizes the spectrum of the microring resonator by detecting the variation of the voltage across the PIN junction of the microring resonator due to the temperature change of the microring resonator, and has the characteristics of simple design process and easy operation.

(2) In the present invention, the PIN junction detects the operating temperature of each micro-ring switch in real time, solves the problem that the number of micro-rings cannot be located, and does not require additional functional devices, and has the advantages of fast temperature detection and low cost. .

DRAWINGS

1 is a block diagram of an apparatus for stabilizing a spectrum of a microring resonator of the present invention;

2 is a voltage-current relationship diagram of a PIN junction as a function of temperature in the microring resonator of FIG. 1. FIG. 3 is a graph showing voltage versus voltage of a PIN junction in the microring resonator of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The specific embodiments of the present invention are described below in conjunction with the drawings in order to provide a better understanding of the invention. Need to pay special attention to the following description, in the description of the function and design When the detailed description of the meter may dilute the main content of the present invention, these descriptions will be omitted here. Embodiment FIG. 1 is a block diagram of a device for stabilizing a microring resonator spectrum of the present invention.

Figure 2 is a graph showing the voltage-current relationship of the PIN junction as a function of temperature in the microring resonator of Figure 1.

Fig. 3 is a graph showing the relationship between the voltage of the PIN junction and the temperature in the microring resonator of Fig. 1.

In the present embodiment, a ridge waveguide structure having a dispersion of 0 at a wavelength of 1.55 um and supporting only a TE base film is exemplified, and a P-type impurity is heavily doped on both sides of the left arm of the ridge waveguide, and is left on the right arm of the ridge waveguide. Focusing on the doping of the N-type impurity and the heavily doped P-type impurity on the right side, in order to increase the conductivity, the intrinsic I region in the middle is lightly doped with the N-type impurity. As shown in FIG. 1, a device for stabilizing the spectrum of a microring resonator includes:

a microring resonator 1, comprising a heater and a PIN junction, is enabled to open or close the microring resonator 1 by a current applied to the PIN junction by the source meter function module 4, and simultaneously detects a temperature change of the microring resonator 1; The signal processing unit 2 includes an amplification, shaping, filtering circuit and a high-precision analog/digital converter (AD) for sequentially inputting the voltage variation Δυ fed back from the source table function module 4 through amplification, shaping, filtering, and input to AD, converting the analog signal into a digital signal and feeding back to the FPGA control unit 3;

An FPGA control unit 3 is configured to generate a switch driving signal of the channel a, and simultaneously receive the digital signal from the signal processing unit 2, and by fitting and analyzing the digital signal, the voltage driving signal of the output b channel, the switch driving signal of the a channel Input to the source table function module 4, the voltage driving signal of the b channel is input to the heater driving unit module 5, the switch driving signal of the a channel is input to the source table function module 4 before the FPGA control unit 3 analyzes the digital signal;

A source meter function module 4, including a current type digital/analog converter (DA) and a voltage follower; the source table function module 4 receives the switch drive signal of the a channel, and converts it into a constant current i through a high precision DA, and then The constant current i is input to the right half arm PIN junction of the microring resonator 1; at the same time, the amount of change AU of the voltage across the PIN junction of the microring resonator caused by the temperature change of the microring resonator 1 is detected, and the voltage change amount AU is fed back. Giving signal processing unit 2;

a heater driving unit 5, comprising a DA and a peripheral matching circuit; after receiving the voltage driving signal of the b channel, the heater driving unit 5 first converts the analog voltage driving signal into high-precision DA, and then passes the analog voltage driving signal through the periphery. The matching circuit performs impedance matching and is loaded into the heater of the microring resonator 1, and the temperature change of the microring resonator 1 is adjusted by changing the voltage generated by the voltage applied across the heater.

In this embodiment, since the processing process of the optical waveguide has an error, in order to make the wave of the microring resonator 1 In the ideal state, a suitable voltage V=4V is applied across the PIP to compensate for the process error by the thermo-optic effect.

Let the temperature fluctuate only in a small range. In the initial state, the microring resonator works stably.

310K, FPGA control unit 3 outputs a switch signal of a channel to the source meter function module 4, which is converted into a constant current of 1 mA by high-precision DA, and input into the PIN junction of the micro-ring resonator, and the current and voltage of the PIN junction The relationship is I = I _s (e ^Vq/kT -l), where I is the current flowing through the PIN junction, 1 is the reverse saturation current, V is the voltage across the PIN, q is the metacharge, and k is the wave The ltzmann constant, T is the absolute temperature of the PIN junction. That is, when the temperature is constant, the current through which the PIN junction passes increases exponentially with voltage; when the temperature rises, as shown in Fig. 2, the IV curve moves upward. At the same time, it can be seen from the above formula that when the input current is constant, the voltage across the PIN junction is linear with the temperature at which it is placed. The output voltage at the temperature of 310K is 0.84V, so the voltage can be judged based on this voltage. Change to get the amount of change in temperature. When the temperature increases, the voltage across it decreases. As shown in Figure 3, the voltage drops by 1.2 mV, indicating a temperature rise of 1K. It is shown in Fig. 3 that as long as the voltage across the PIN junction is detected, temperature information can be obtained, and the voltage and temperature have a good linearity, which ensures the reliability and accuracy of the temperature of the PIN junction detecting microring resonator 1.

When the temperature rises by 1K, the voltage across the PIN junction will drop by 1.2mV. This voltage change Δυ is input to the FPGA control unit 3 through the signal processing unit 2, and the relationship between the voltage and temperature stored in the FPGA in advance can be analyzed by the FPGA. The extent to which this temperature has dropped. In the silicon-based material, the thermal conductivity of silicon is 1.49 W/(cm*IQ, and the size of the microring is 10 um. In order to lower the temperature by 1 K, the heat generated by the PIP heater needs to be reduced by about 0.3278 mW. In this embodiment In the design, the impedance of the PIP heater is about 10k ohms. In order to generate 0.3278mW of energy, the voltage across the PIP heater needs to be reduced by 0.4V, that is, the voltage drive signal of the b channel is sent from the FPGA control unit 3. To the heater driving unit 5, the voltage across the PIP heater is 3.6V, and as the heat decreases, the temperature continues to decrease, and the voltage driving signal of the b channel sent by the FPGA control unit 3 gradually increases. Go back to the initial state.

When the temperature drops by 1K, the voltage across the PIN junction is increased by 1.2mV. After the analysis of the FPGA, the voltage across the PIP heater is increased by 0.4V, that is, the heating voltage becomes 4.4V, and the additional heat generated causes the temperature to rise. high. When the temperature rises by 0.5K due to heating, the voltage across the PIN is reduced by 0.6 mV. At this point, only an additional amount of heat of 0.1639 mW is generated, and the heating voltage becomes 4.2V. The temperature gradually rises, the detected voltage changes decrease, the heating voltage gradually decreases, and finally approaches equilibrium. It can be seen from the above that the design of the high-precision circuit eliminates the influence of temperature changes on the micro-ring spectrum, and obtains a stable micro-ring optical switch spectrum. Since the PIN junction and PIP heater can be integrated in a single micro-ring switch, accurate control of each micro-ring is achieved.

While the invention has been described with respect to the preferred embodiments of the present invention, it should be understood that These variations are obvious as long as the various changes are within the spirit and scope of the invention as defined and claimed in the appended claims, and all inventions that utilize the inventive concept are protected.

Claims

claims

1. A device for stabilizing the spectrum of a microring resonator, which is characterized by including:

A micro-ring resonator, including a heater and a PIN junction. The current loaded to the PIN junction through the source meter function module enables the micro-ring resonator to be turned on or off, and at the same time detects the temperature change of the micro-ring resonator;

A signal processing unit, including amplification, shaping, filtering circuits and a high-precision analog/digital converter (AD), used to amplify, shape, and filter the voltage variation U fed back by the source meter function module in sequence and then input it to the high-voltage Precision analog/digital converter (AD) converts analog signals into digital signals and feeds them back to the FPGA control unit;

An FPGA control unit, used to generate the switch drive signal of channel a, and at the same time receive the digital signal from the signal processing unit, and output the voltage drive signal of channel b by fitting and analyzing the digital signal; the switch drive signal of channel a is input to Source meter function module, the voltage drive signal of channel b is input to the heater drive unit module;

A source meter function module, including a current-type digital/analog converter (DA) and a voltage follower; after receiving the switch drive signal of channel a, the source meter function module converts it into a constant current i through high-precision DA, and then converts the constant current i The current i is input to the right half-arm PIN junction of the micro-ring resonator; at the same time, the change amount ΔΙΙ of the voltage at both ends of the micro-ring resonator PIN junction caused by the temperature change of the micro-ring resonator is detected, and the voltage change amount ΔΙΙ is fed back to the signal processing unit ;

A heater drive unit, including DA and peripheral matching circuit; after receiving the voltage drive signal of channel b, the heater drive unit first converts it into an analog voltage drive signal through high-precision DA, and then passes the analog voltage drive signal through the peripheral matching circuit After achieving impedance matching, the heater loaded into the microring resonator generates heat by changing the voltage loaded to both ends of the heater to adjust the temperature change of the microring resonator; after the device is started, the FPGA control unit outputs _a switch drive signal to the source. The meter function module generates a constant current i after being converted by DA in the source meter function module, and then inputs the constant current into the right half-arm PIN junction of the microring resonator to control the opening or closing of the microring resonator; the PIN junction controls the input current Finally, the temperature change amount of the micro-ring resonator can be detected, and the change amount ΔΙΙ of the voltage at both ends of the PIN junction of the micro-ring resonator caused by the temperature change is obtained. The voltage change amount ΔΙΙ is amplified, shaped, filtered, and AD processed by the signal processing unit. Finally, the digital signal is obtained, and the digital signal is input to the FPGA control unit. After fitting and analysis, the voltage drive signal of the output channel b is loaded to the heater drive unit module. The voltage drive signal of channel b is converted by the DA of the heater drive unit. Generates analog voltage drive signals to match the periphery of the heater drive unit After the circuit achieves impedance matching, it is loaded into the heater of the microring resonator. By changing the voltage applied to both ends of the heater, heat is generated to adjust the temperature change of the microring resonator, thereby maintaining the spectral stability of the microring resonator.

2. The device for stabilizing the spectrum of a microring resonator according to claim 1, characterized by comprising: the switch driving signal of path a is input to the source meter function module before the FPGA control unit analyzes the digital signal.