微环波长锁定电路的研究

… temperature control to tune their resonant wavelength [9]. In this work, we present a radiation-tolerant Thermal Control Unit (TCU) for micro-ring modulators. The proposed TCU includes …

… the majority of the circuitry devoted to wavelength locking (Fig. 3, … circuitry can then be estimated to be 385 µW. To express this in the popular fJ/bit metric we assume that the microring …

… output of the microring heater PH to wavelength-lock the ring to a lock point. Suppose Lopt … ) during lock point selection and Ltrack is the value the controller tracks to maintain lock. …

… 1 shows a simplified experimental setup and circuitry used for wavelength locking. The top … The wavelength-locking circuitry will work with other types of microring devices [10]. The …

We propose and experimentally demonstrate a self-homodyne locking method for a silicon microring resonator (MRR). The device employs a self-homodyne detection structure and consists of a tunable MRR with two directional couplers along the ring for monitoring, two phase shifters to calibrate the phase difference between the two monitored optical signals, and a Y-branch to combine the two signals. A single photodetector is used to detect the output power of the Y-branch. If the MRR is on resonance, a destructive interference occurs in the Y-branch, therefore the monitored photocurrent is minimized. By using such a device structure and the homodyne detection scheme, the MRR with a Q factor of 1.9 × 104 can be accurately locked to the signal wavelength, and the locking process is insensitive to input power variation. The wavelength locking range is larger than one free spectral range (FSR) of 6 nm, and the locking errors are ≤0.015 nm.

This paper proposes an electronic-photonic converged adaptive-tuning-step (ATS) pipelined time-division-multiplexing (PTDM) scheme to achieve fast wavelength locking of multiple micro-ring resonators (MRRs) using a shared controller without deteriorating the locking accuracy. The ATS technique breaks the trade-off between wavelength tracking speed and locking accuracy. The PTDM control enables controller sharing while maintaining a high loop bandwidth by exploiting the speed mismatch between the heater and the controller. Custom-designed integrated circuits provide interfacing and clocking functions. A hybrid-integrated four-channel prototype of the proposed scheme has demonstrated a record-breaking tracking speed of 180 nm/s with a locking accuracy of about 7 pm and a tuning range of about 9 nm. This scheme could be extended to applications with dozens or even hundreds of MRRs.

Thermal cross-talk can impair the efficiency of tuning algorithms employed for the control, calibration and reconfiguration of photonic integrated circuits (PICs). For example, in coupled microring resonator (MRRs) architectures, thermal crosstalk is responsible for an unwanted coupling among the round-trip phases of the resonators, thus affecting their resonance frequencies. Here we propose a novel approach, named Transform Coordinate method (TCM), enabling thermal cross-talk cancellation in PICs. In the TCM, instead of controlling the phase shift of each photonic element individually, the eigensolutions of the thermally coupled system are calculated and employed as control variables. The effectiveness of the TCM is demonstrated by implementing a feedback control system providing automatic resonance tuning of 3rd order coupled MRR filters. Numerical simulations, confirmed by experimental results achieved on a high-index-contrast silicon oxynitride (SiON) platform, demonstrate that the TCM enables a tuning process that is faster, more accurate and more robust with respect to conventional methods based on individual tuning of each MRR. Further, the TCM can be used as a wavelength locking algorithm to maintain the tuned condition in the presence of temperature drift as well as random fluctuations of the wavelength and of the power of the input signal. Finally, the TCM can be applied to generic PIC architectures based on arbitrary combinations of MRRs and other integrated interferometric devices.

… of locking and reference level adjustment until the loop “over-searches” and can no longer lock … level to obtain thefinal lock point near the target resonance wavelength and achieve an …

… wavelength locking of a hybrid CMOS-silicon photonics ring-based transmitter using a 40 nm CMOS circuit … photonic transceiver circuits with microring resonator bias-based wavelength …

… 37.6nm wavelength range and wavelength locking to account for a … ring resonator-based circuits consisting of many microrings. … , “Wavelength locking and thermally stabilizing microring …

Microring resonator (MRR) is a versatile photonic device that finds a wide range of applications in communication, computing, and sensing. However, it is susceptible to fabrication, thermal, and laser wavelength variations. This paper presents a PWM wavelength locker for a MRR. The wavelength locker and the MRR have been fabricated in a monolithic photonic BiCMOS platform. The effectiveness of this design is verified by extensive computer simulations. To the best of our knowledge, this is the first closed-loop PWM wavelength locker for MRRs reported in the literature.

This paper presents a novel approach to addressing the issue of temperature-induced instability in an optical, single-sideband transmitter based on a micro-ring resonator (MRR) suitable for millimeter-wave (mmW) radio-over-fiber (RoF) communications. We propose utilizing the drop port of the MRR to provide a feedback signal to the closed-loop control (CLC) system. The latter serves to maintain the optimal alignment between the laser’s carrier and the MRR’s resonant wavelength, thus mitigating the adverse effects of chromatic-dispersion-induced power fading at the receiving end. Since the feedback information is extracted from the otherwise-wasted resonant energy at the drop port, the control system does not compromise the delicate optical signal at the through port. A CLC was synthesized, designed, and prototyped to provide real-time wavelength tuning of the heat-pump-controlled laser based on the feedback signal. Experimental evaluations demonstrate that the wavelength of the laser could be successfully locked to the MRR’s resonance with a wavelength dither of less than 0.004 nm (~491 MHz). This allowed us to limit the power-penalty deterioration to less than 2 dB for a RoF link with a 2.5-km standard telecommunication single-mode fiber (SMF), a modulation frequency of 37.8 GHz, and a carrier wavelength of 1563.97 nm (~191.820 THz). The proposed solution offers an alternative approach for the carrier and the MRR’s resonant wavelength interlocking without the need for complex photonics like thermo-optic or electro-optic structures to control the temperature or phase velocity, respectively.

Micro-ring resonator (MRR) is a key photonic device that has a wide range of applications but suffers from wavelength uncertainties. For almost all practical applications, a wavelength controller is required for each MRR. The wavelength controller is usually much larger than the MRR. With more complicated control algorithms, the controller size becomes even larger. Equipping each MRR with a wavelength controller will not be scalable. We propose a pipelined time-division-multiplexing (PTDM) control scheme that achieves high scalability while maintaining good loop bandwidth by exploiting the speed mismatch between the heater and the controller. To verify this proposed scheme, a hybrid integrated controller supporting four MRRs is designed. Measurement results show that it achieves a sine tracking speed of about 15 nm/s while achieving a locking accuracy of 7 pm and a tuning range of 9 nm.

… This paper presents a multi-channel hybrid-integrated photonic receiver based on microring drop filters and waveguide photodetectors implemented in a 130 nm SOI process and high-…

A microring modulator array coupled to a common bus waveguide can be used to construct low power, compact and flexible wavelength-division-multiplexing (WDM) transmitters. However, due to extremely small working bandwidths of the rings, it is challenging to find the right resonant wavelength setting and locking the resonance to an external laser. In the paper, we propose a novel technique enabling simultaneous wavelength locking of a microring modulator array with a single monitor, together with automatically optimizing the wavelength setting. We experimentally demonstrate locking three rings over a temperature range >40 °C at 3x20 Gb/s on-off-keying (OOK) modulation and ~3x75 Gb/s discrete multi-tone (DMT) modulation.

We demonstrate that n-doped resistive heaters in silicon waveguides show photoconductive effects with high responsivities. These photoconductive heaters, integrated into microring resonator (MRR)-based filters, were used to automatically tune and stabilize the filter's resonance wavelength to the input laser's wavelength. This is achieved without requiring dedicated defect implantations, additional material depositions, dedicated photodetectors, or optical power tap-outs. Automatic wavelength stabilization of first-order MRR and second-order series-coupled MRR filters is experimentally demonstrated. Open eye diagrams were obtained for data transmission at 12.5 Gb/s while the temperature was varied by 5 °C at a rate of 0.28 °C/s. We theoretically show that series-coupled MRR-based filters of any order can be automatically tuned by using photoconductive heaters to monitor the light intensity in each MRR, and sequentially aligning the resonance of each MRR to the laser's wavelength.

We propose and demonstrate active resonance wavelength stabilization for silicon microring resonators with an in-resonator defect-state-absorption (DSA)-based photodetector (PD) for optical interconnects. We integrate an electro-optic (EO) tuner and a thermo-optic (TO) tuner on the microring, which are both feedback-controlled following a photocurrent threshold-detection method. Our BF(2)-ion-implanted DSA-based PIN PD exhibits a cavity-enhanced sub-bandgap responsivity at 1550 nm of 3.3 mA/W upon -2 V, which is 550-fold higher than that exhibited by an unimplanted PIN diode integrated on the same microring. Our experiment reveals active stabilization of the resonance wavelength within a tolerance of 0.07 nm upon a step increment of the stage temperature by 7 °C. Upon temperature modulations between 23 °C and 32 °C and between 18 °C and 23 °C, the actively stabilized resonance exhibits a transmission power fluctuation within 2 dB. We observe open eye diagrams at a data transmission rate of up to 30 Gb/s under the temperature modulations.

As the rapid development of silicon photonics, high-Q silicon microring resonators (MRRs) have been extensively used in the integrated microwave photonic systems. However, one major hurdle to be overcome is that the resonant wavelengths of MRR are highly sensitive to the chip temperature. Herein, a frequency stabilized optoelectronic oscillator (OEO) based on an ultra-high-Q silicon MRR is proposed and experimentally demonstrated. The frequency stabilization is realized by using a home-made feedback control loop based on threshold-detection method to stabilize the resonant wavelengths of the MRR. By using the frequency-stabilization technique, the measured frequency jitter of the MRR based OEO is reduced from 50 MHz to 85 kHz in 10 minutes. The oscillating frequency of the proposed OEO can be also tuned between 0 and 20 GHz. By designing and fabricating the MRR with cascaded multi-mode and single-mode waveguides, the measured Q factor of the fabricated MRR is as high as 1.13 × 106. The corresponding phase noise of the microwave signal at 10 kHz offset frequency is −95 dBc/Hz when the microwave signal is 12.23 GHz. During the oscillating frequency tuning, the side-mode suppression ratio (SMSR) remains above 50 dB. The proposed MRR-based OEO with long-term stability has the potential to be monolithically integrated.

… stabilize the temperature of a microring resonator it must be interfaced with control circuitry. In addition to thermally stabilizing the microring resonator, … relevant microring resonators with …

… This paper presents the design of two different control approaches for stabilizing the operating point of a microring resonator modulator (MRM) when fast disturbances occur. These …

Thermal actuators are among the most consolidated and widespread devices for the active control of photonic integrated circuits (PICs). As a main drawback, mutual thermal crosstalk among actuated devices integrated onto the same photonic chip can affect the working point of the PIC and can reduce the efficiency of automated tuning and calibration procedures. In this paper, a strategy to cancel out the effects of the phase coupling induced by thermal crosstalk is presented. In our technique, we named thermal eigenmode decomposition (TED), all the actuators of the PIC are controlled simultaneously according to the eigensolution of the thermally coupled system. The effectiveness of the TED method is validated by numerical simulations and experiments carried out on coupled microring resonator and switch fabrics of Mach–Zehnder interferometers. With respect to individual control of phase actuators, where thermal crosstalk can hinder the convergence of automated tuning algorithms, with the TED technique convergence is always reached, requires a lower number of iterations, and is less sensitive to the initial state of the PIC. The proposed TED method can be applied to generic tuning and locking algorithm, can be employed in arbitrary PIC architectures and its validity can be extended to systems where phase coupling is induced by other physical effects, such as mutual mechanical stress and electromagnetic coupling among RF lines.

We investigate and demonstrate the thermal crosstalk problem in integrated photonic circuits with metal and silicon doped heaters. Further, we illustrate that due to the localized heating effect, integrated doped heaters are out-performed in terms of thermal crosstalk as compared to integrated metal heaters. To mitigate thermal crosstalk and enhance phase tuning efficiency further, a CMOS compatible air-filled trench region is realized between the doped heater and the adjacent element. The performances of three fundamental building blocks of integrated photonic circuits, namely, a PN phase shifter, an optical attenuator, and a ring resonator, are tested by full-wave thermal, charge, and optical simulations. Additionally, the impact of thermal crosstalk on the performance of integrated PN phase shifters and optical attenuators is examined thoroughly. The proposed low crosstalk thermal phase shifters might be very beneficial for densely routed complex integrated photonic circuits like photonic transceivers for data centers, optical phased array antennas, and photonic reservoirs.

This paper demonstrates the possibility of automatically stabilizing the working condition of an integrated Silicon Photonics microring modulator with a novel dithering-based control scheme. The proposed feedback strategy leverages a real-time acquisition of the modulator non-linear transfer function (TF) and operates by setting the target locking point to the zero of the TF second derivative, i.e. where the ring slope is maximum. This results in a control algorithm that is both power-independent and calibration-free. The paper shows that the operating point identified in this way has a negligible difference with respect to the optimum working condition of minimum Transmitter Penalty normally targeted and that the employed dithering signal does not affect the modulation quality. The control performances, made possible by an FPGA-based platform ensuring a 30 ms response time, are assessed in a 50 Gbit/s routing scenario, demonstrating effective compensation of wavelength and thermal variations and successful transmission even in demanding environments.

Microring weight banks present novel opportunities for reconfigurable, high-performance analog signal processing in photonics. Controlling microring filter response is a challenge due to fabrication variations and thermal sensitivity. Prior work showed continuous weight control of multiple wavelength-division multiplexed signals in a bank of microrings based on calibration and feedforward control. Other prior work has shown resonance locking based on feedback control by monitoring photoabsorption-induced changes in resistance across in-ring photoconductive heaters. In this work, we demonstrate continuous, multi-channel control of a microring weight bank with an effective 5.1 bits of accuracy on 2Gbps signals. Unlike resonance locking, the approach relies on an estimate of filter transmission versus photo-induced resistance changes. We introduce an estimate still capable of providing 4.2 bits of accuracy without any direct transmission measurements. Furthermore, we present a detailed characterization of this response for different values of carrier wavelength offset and power. Feedback weight control renders tractable the weight control problem in reconfigurable analog photonic networks.

A method to stabilize the resonance wavelength of a depletion-type silicon micro-ring resonator modulator during high-speed operation is described. The method utilizes the intrinsic defect-mediated photo-absorption of a silicon waveguide and results in a modulator chip fabrication process that is free of heterogeneous integration (for example using germanium), thus significantly reducing the complexity and cost of manufacture. Residual defects, present after p-n junction formation, are found to produce an adequate photocurrent for use as a feedback signal, while an integrated heater is used to compensate for thermal drift via closed-loop control. The photocurrent is measured by a source-meter, which simultaneously provides a DC bias to the integrated heater during high-speed operation. A drop-port or an integrated extrinsic detector is not needed. This feedback control method is experimentally demonstrated via a computer-aided proportional-integral-differential loop. The resonance locking is validated for 12.5 Gb/s intensity modulation in a back-to-back bit-error-rate measurement. The stabilization method described is not limited to a specific modulator design and is compatible with speeds greatly in excess of 12.5 Gb/s, in contrast to the bandwidth limitation of other stabilization methods that rely on intrinsic photo-carrier generation through non-linear processes such as two-photon-absorption. Further, the use of intrinsic defects present after standard fabrication insures that no excess loss is associated with this stabilization method.

Given the escalation of demand for high-speed data interconnection, both between users and datacenters, high-capacity optical networks need a boost in capacity, flexibility, and efficiency. To stand up for those problems, the network reconfigurability is a key feature in a saturated and power hungry network operating scenario. In this paper, a reconfigurable optical node, using a commercial integrated photonics foundry, was conceived, fabricated, and tested. A novel application of automatic control of complex optical circuits involving locking and tuning of microring resonators is presented. The technique exploits a channel labeling strategy to identify a single optical channel amid a dense wavelength division multiplexing comb. The fabricated filter array provided add–drop ports with hitless channel reconfiguration and telecom graded specifications as 20 dB of in-band isolation, 40 GHz of channel bandwidth in a microring filter with 1 THz of free spectral range.

We report the first complete 10G silicon photonic ring modulator with integrated ultra-efficient CMOS driver and closed-loop wavelength control. A selective substrate removal technique was used to improve the ring tuning efficiency. Limited by the thermal tuner driver output power, a maximum open-loop tuning range of about 4.5nm was measured with about 14mW of total tuning power including the heater driver circuit power consumption. Stable wavelength locking was achieved with a low-power mixed-signal closed-loop wavelength controller. An active wavelength tracking range of > 500GHz was demonstrated with controller energy cost of only 20fJ/bit.

As photonics moves from the single-device level toward large-scale, integrated, and complex systems on a chip, monitoring, control, and stabilization of the components become critical. We need to monitor a circuit non-invasively and apply a simple, fast, and robust feedback control. Here, we show non-invasive monitoring and feedback control of high-quality-factor silicon (Si) photonic resonators assisted by a transparent detector that is directly integrated inside the cavity. Control operations are entirely managed by a CMOS microelectronic circuit that is bridged to the Si photonic chip and hosts many parallel electronic readout channels. Advanced functionalities, such as wavelength tuning, locking, labeling, and swapping, are demonstrated. The non-invasive nature of the transparent monitor and the scalability of the CMOS readout system offer a viable solution for the control of arbitrarily reconfigurable photonic integrated circuits aggregating many components on a single chip.

… We first characterized the microring with the TFSC disabled and measured a thermal drift of 74 pm/C. We then confirm the maximum TFSC output voltage of 5 V corresponding to a …

… wavelength drift at time t, Δλcarrier(t). We do not consider the abrupt carrier wavelength drift due to … We model ΔT(t) in terms of an equivalent circuit comprising a thermal capacitance CT …

We present a real-time approach for stabilizing a III-V/Si hybrid external-cavity laser implemented using microring monitoring and a feedback control loop. Laser mode stabilization over bias current and stage temperature variations are experimentally demonstrated. We achieved single-mode and mode-hop-free laser operation as the bias current was swept across 320 mA. The same feedback control also enabled wavelength-locked laser operation using an intracavity phase control. The feedback control was also applied to an integrated on-chip hybrid laser, and mode-hop-free laser operation was demonstrated over 23 °C substrate temperature variation.

Microring modulators (MRMs) with CMOS electronics enable compact low power transmitter solutions for 400G Ethernet and co-packaged optical transceivers. In this article, we present a 3-D-integrated 112-Gb/s pulse amplitude modulation (PAM)-4 optical transmitter (OTX) using silicon photonic MRM, on-chip laser, and co-packaged 28-nm CMOS driver. The 3- $V_{\mathrm {pp}}$ driver includes a lookup table (LUT)-based PAM-4 nonlinear equalizer to address static and dynamic MRM nonlinearities. An integrated thermal control method that is insensitive to input power fluctuations is proposed to compensate for the temperature sensitivity of MRMs. PAM-4 measurement results of our OTX at 112 Gb/s show that transmitter dispersion eye closure quaternary (TDECQ) < 1.5 dB is achieved from 28 °C to 55 °C with 7.4-pJ/bit energy efficiency including on-chip laser.

This paper presents a microring resonator-based weight function for neuromorphic photonic applications achieving a record-high precision of 11.3 bits and accuracy of 9.3 bits for 2 Gbps input optical signals. The system employs an all-analog self-referenced proportional-integral-derivative (PID) controller to perform real-time temperature stabilization within a range of up to 60 <inline-formula><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula>C. A self-calibrated weight function is demonstrated for a range of 6 <inline-formula><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula>C with a single initial calibration and minimal accuracy and precision degradation. By monitoring the through and drop ports of the microring with variable gain transimpedance amplifiers, accurate and precise weight adjustment is achieved, ensuring optimal performance and reliability. These findings underscore the system's robustness to dynamic thermal environments, highlighting the potential for high-speed reconfigurable analog photonic networks.

This work presents a hybrid-integrated 4-<inline-formula> <tex-math notation="LaTeX">$\lambda $ </tex-math></inline-formula> micro-ring modulator-based wavelength-division multiplexed (WDM) optical transmitter (OTX) in the O-band, suitable for co-packaged optics. It supports up to 112 Gb/s per wavelength using high-bandwidth micro-ring modulators (MRMs) together with nonlinear equalization in the driver electronics. A thermal control scheme using MRM photocurrent to sense process and temperature variations is implemented, enabling <0.05 dB TDECQ penalty over 10 °C. This compact photocurrent-based control method significantly reduces the hardware and packaging overhead required for ring-based WDM transceivers. Measurements from a 4-<inline-formula> <tex-math notation="LaTeX">$\lambda $ </tex-math></inline-formula> OTX with 28-nm CMOS electronic IC (EIC) and custom silicon photonic IC (PIC) show the OTX supports 112 Gb/s with <0.7 dB TDECQ across all four channels while dissipating 5.8 pJ/bit in the electronics.

… this experiment with an average drift of 0.28 pm over an hour. This drift corresponds to 10-mK … With the PID temperature controller circuit, we show the stability of the microring resonator …

… Thermal variation causes a microring to respond to a … shift the resonance wavelength of a microring by as much as 0.1 nm, … of a microring to overcome both thermal drift and fabrication …

… to tune the output power and wavelength of microring lasers, with … laser sources and Si photonic circuits, and show the … a Si bus waveguide to an on-chip hybrid photodetector (PD) at …

… optical filter based on planner lightwave circuit (PLC) without … a simple and efficient on-chip interrogation system should be … resonance of the microring filter and thermally tuning the filter …

We report on a packaged prototype of a WDM photonic transceiver. It is an all-solid state hybrid assembly based on 130nm SOI photonic circuitry integrated with a 40nm CMOS VLSI driver. Our prototype supports eight tunable WDM channels operating at 10Gb/s, each capable of both transmitting and receiving data on the same chip. We discuss two options to close the link using the optical fiber or a waveguide bridge chip. We provide integration details and supporting link measurement data to describe packaged photonic module and its power efficient functionality with its on-chip power per channel averaging 1.3pJ/bit, excluding off-chip laser electrical power.