Fast Tunable Laser Research Articles

Research on flexible and fast tunable laser in coherent optical communications

A flexible and fast tunable laser based on hybrid integration is proposed, which can realize single and multi-wavelength reconfigurable output by controlling the on or off of semiconductor optical amplifiers (SOAs) array in combination with a tunable arrayed waveguide grating (AWG). The wavelength switching time achieves <0.8 ns. The stable output power of the tunable laser is >16 dBm with >70 dB side mode suppression ratio (SMSR) and 6.4 nm tunability. The designed laser exhibits narrow linewidths down to 1 kHz and longitudinal mode spacing of 0.8 nm, which is suitable for ITU-T standards and the output power meets the requirements of coherent optical communications. A broadened spot-size converter (SSC) for bi-directional transmission is designed and implemented with a power coupling efficiency about 0.93 and an optical bandwidth of more than 200 nm. Demonstration of the 100 Gb/s quadrature phase shift keying (QPSK) self-homodyne coherent optical transmission based on designed laser is achieved.

Widely and fast tunable external cavity laser on the thin film lithium niobate platform

We develop an integrated external cavity laser with a broad wavelength tuning range and a fast switching speed on thin film lithium niobate (TFLN) platform. By butt coupling an InP-based optical gain chip with a TFLN external cavity chip, a hybrid lithium niobate/III-V tunable laser with a wavelength switching speed of 18 ns is achieved. Furthermore, using a cascaded external cavity filter composed of three micro-ring resonators (MRRs), the laser features an ultra-wide wavelength tuning range of 96 nm across the C + L + U bands, which is the greatest value known for tunable lasers integrated on TFLN. The maximum laser output power is 0.98 mW, with a measured side mode suppression ratio (SMSR) of better than 52 dB. The laser we developed is critical in applications such as optical sensors and wavelength routed optical switch.© 2023 xxxxxxxx. Hosting by Elsevier B.V. All rights reserved.

Low-latency wavelength-switched clock-synchronized intra-data center interconnects enabled by hollow core fiber.

Fast (nanoseconds) optical wavelength switching is emerging as a viable solution to scaling the size and capacity of intra-data center interconnection. A key enabling technology for such systems is low-jitter optical clock synchronization, which enables sub-nanosecond clock and data recovery for optically switched frames using low-cost methods such as clock phase caching. We propose and demonstrate real-time low-latency wavelength-switched clock-synchronized intra-data center interconnection at 51.2 GBd using a fast tunable laser (with ns scale switching time) and ultra-stable-latency hollow core fiber (HCF) for optically-switched data center networks. For wavelength-switched systems, we achieve a physical layer latency below 46 ns, consisting of 28 ns transceiver latency and a 18 ns inter-packet gap. Finally, we show that by exploiting the low chromatic dispersion and thermally-stable latency features of HCF, active clock phase tracking can be entirely eliminated.

Nanosecond tunable laser for the all-optical switching network.

The optically switched network can offset the increasing gap between datacenter traffic growth and electrical switch capacity due to the slowdown of Moore's law. Ultra-high-speed wavelength tunable lasers are especially vital for the high integration and performance improvement of the all-optical switching system. In this paper, a fast tunable laser based on a laser array is realized. The 2×8 matrix structure of the laser array is fabricated by the reconstruction-equivalent-chirp (REC) technique. Aiming at the 2×8 array, a drive control system is designed to provide stable and fast switching, to achieve high-speed switching of the laser wavelength, and to keep the wavelength stable after switching. The simulation and experimental results show that the switching time between any two wavelength channels of the laser is less than 10ns. The switching time of any two channels of the laser can be reduced by 2-3ns after the pre-emphasis processing of the electrical signal.

Tunable Narrow-Linewidth Fiber Laser Based on the Acoustically Controlled Polarization Conversion in Dispersion Compensation Fiber

Researches on high coherence light sources always pursue fast tuning speed, linear tunability and persistence of narrow linewidths at different tuning channels. Fortunately, acousto-optical interaction (AOI) can be employed in the fast management of the lasing wavelength. Herein, we propose a fast tunable narrow-linewidth fiber laser assisted by the acoustically-induced polarization selection in dispersion compensation fiber (DCF). The lasing wavelength is determined by the acoustically-induced band-pass grating in DCF. The large dispersion slope of the DCF suppresses the bandwidth of the TM₀₁ peak to be less than 1 nm. The acousto-optic-controlled polarization conversion effectively restrains the acousto-optic frequency shift. With side longitudinal mode suppressions induced by the combintion of the self-injection feedback and saturable absorption filtering, the output laser successfully achieves the narrow-linewdith operation and owns a low relative intensity noise floor of &#x2212;135 dB&#x002F;Hz. By controlling the acoustic-wave frequency, the laser can be linearly tuned with a large wavelength range (over 20 nm, linear fitting R² reaches 0.99781), and the laser linewidths remain about &#x223C;2 kHz in different tuning channels. The laser tuning dynamics under the acousto-optical controlling are experimentally revealed, and the lasing tuning response time is &#x223C;800 &#x03BC;s.

Fast interrogation of dynamic low‐finesse Fabry‐Perot interferometers: A review

AbstractLow‐finesse fiber‐optic Fabry–Perot (F‐P) interferometric sensor has the advantages of high sensitivity, anti‐electromagnetic interference, and compact size, and is one of the most widely used optical fiber sensors. With the development of sensor design and demodulation algorithms, F‐P sensing technique plays an increasingly important role in high‐speed dynamic measurement, such as dynamic temperature or pressure, acoustic vibration, dynamic displacement, and distance. Signal demodulation methods largely determine the performance of the entire sensing system. Compared with quasi‐static measurement, high‐precision measurement of dynamic F‐P cavity is more challenging. The advancement of fast tunable laser technology in telecommunication field provides novel perspectives for demodulation methods and dynamic applications based on F‐P sensors. This article reviews the latest developments in fast interrogation techniques for dynamic low‐finesse F‐P sensors, including intensity demodulation, quadrature phase demodulation and absolute cavity length demodulation. In addition, array multiplexing and multi‐parameter measurement techniques are also involved.

Proof-of-Concept of the Time and Spectral Optical Aggregation Network

In this article, we present the proof of concept (PoC) of the time and spectral optical aggregation (TISA) approach that allows a better filling of the time and spectral resources of an optical transport network. Some innovative solutions have been implemented, such as a new and fast tunable laser that permits to color the bursts sent in the TISA network, as well as their transmission with both DP-QPSK and DP-16QAM coherent multi-band (MB) OFDM formats. BER versus OSNR measurements have been achieved showing less than 1-dB penalty in back-to-back or after transmission. The tolerance of bursts against frequency mismatch occurring between the transceiver and the optical filter that extracts a sub-band inside the MB-OFDM signal has also been evaluated, and ∼1.5 GHz tolerance has been measured for bursts of ∼6.7 GHz bandwidth. Furthermore, in order to mitigate the transients in the coherent receiver that faces alternatively the presence or absence of signal, a novel channel estimator based on a sliding window has been introduced. Its efficiency and performance has been experimentally validated, and its ability to suppress the error threshold of the BER versus OSNR curves has been demonstrated. By the experimental proof of concept delivered here, the ability of the TISA network to perform with a good level of performance the transparent routing and sub-wavelength aggregation/disaggregation in the time and spectral domains simultaneously has been established. Beyond the important and crucial aspect of the optimal filling of the optical resources, our PoC demonstrate the ability of the TISA approach to push the flexibility of an optical transport network at its limit while allowing a cost and power consumption limitation obtained by the removal of costly and power-hungry optical-electrical-optical regenerators.

Interband Cascade Laser Arrays for Simultaneous and Selective Analysis of C1-C5 Hydrocarbons in Petrochemical Industry.

The detection and measurement of hydrocarbons are of high interest for a variety of applications, for example within the oil and gas industry from extraction throughout the complete refining process, as well as for environmental monitoring and for portable safety devices. This paper presents a highly sensitive, selective, and robust tunable laser analyzer that has the capability to analyze several components in a gas sample stream. More specifically, a multi-gas system for simultaneous detection of C1 to iC5 hydrocarbons, using a room temperature distributed feedback interband cascade laser array, emitting in the 3.3 µm band has been realized. It combines all the advantages of the tunable laser spectroscopy method for a fast, sensitive, and selective in-line multicomponent tunable laser analyzer. Capable of continuous and milliseconds fast monitoring of C1-iC5 hydrocarbon compositions in a process stream, the analyzer requires no consumables (e.g., purging, carrier gas) and no in-field calibration, enabling a low cost of ownership for the analyzer. The system was built based on an industrial GasEye series platform and deployed for the first time in field at Preem refinery in Lysekil, Sweden, in autumn 2018. Results of the measurement campaign and comparison with gas chromatography instrumentation are presented.

LSTM-Based Traffic Load Balancing and Resource Allocation for an Edge System

The massive deployment of small cell Base Stations (SBSs) empowered with computing capabilities presents one of the most ingenious solutions adopted for 5G cellular networks towards meeting the foreseen data explosion and the ultralow latency demanded by mobile applications. This empowerment of SBSs with Multi-access Edge Computing (MEC) has emerged as a tentative solution to overcome the latency demands and bandwidth consumption required by mobile applications at the network edge. The MEC paradigm offers a limited amount of resources to support computation, thus mandating the use of intelligence mechanisms for resource allocation. The use of green energy for powering the network apparatuses (e.g., Base Stations (BSs), MEC servers) has attracted attention towards minimizing the carbon footprint and network operational costs. However, due to their high intermittency and unpredictability, the adoption of learning methods is a requisite. Towards intelligent edge system management, this paper proposes a Green-based Edge Network Management (GENM) algorithm, which is an online edge system management algorithm for enabling green-based load balancing in BSs and energy savings within the MEC server. The main goal is to minimize the overall energy consumption and guarantee the Quality of Service (QoS) within the network. To achieve this, the GENM algorithm performs dynamic management of BSs, autoscaling and reconfiguration of the computing resources, and on/off switching of the fast tunable laser drivers coupled with location-aware traffic scheduling in the MEC server. The obtained simulation results validate our analysis and demonstrate the superior performance of GENM compared to a benchmark algorithm.

Experimental Demonstration of a Photonic Frame Based Packet-Switched Optical Network for Data Centers

This article reports on the design and the experimental realization of packet-switched optical network (PSON) for a data center network. In PSON, an optical interconnect consists of a combination of a fast tunable laser (FTL), an arrayed waveguide grating router, and a burst mode receiver (BMR). The conventional FTL transmitters can only accommodate short fixed-size photonic frame (PF) of tens of microseconds rather than variable-size PF due to the short-term wavelength stability. By using the FTL with a thermal compensation method, the PSON can support variable-size PFs with extended size to minimize the switching overhead in the optical switch domain. Our PSON system can achieve up to 96% throughput of 10 GbE service as the end-to-end optical switching time is reduced to 1.94 $\mu$ s that requires only 3 $\mu$ s guard-time in a 45 $\mu$ s time-slot. Total switching time includes wavelength conversion time of FTL, response time of BMR and burst mode-clock and data recovery (BM-CDR). Our PSON will achieve near non-blocking scheduling by use of a centralized scheduler running a grant-aware (GA) scheduling algorithm, which can be further improved to be non-blocking scheduling with a novel algorithm called C-RRP. The C-RRP scheduling algorithm is designed especially for the non-uniform distribution. Simulation results show that C-RRP improves the throughput and latency performance in hot-spot conditions.

CBOSS: Bringing Traffic Engineering Inside Data Center Networks

Today’s traditional, hierarchical, fullelectronic data centers cannot guarantee quality of service (QoS) for latency-sensitive applications or carrier-grade multitenancy.We propose cloud burst optical-slot switching (CBOSS), an intra-data center network architecture leveraging the original optical components and custom software- defined network (SDN) control to enable traffic engineering. In particular, we demonstrate network slicing on demand with subwavelength granularity and deterministic per-flowQoSguarantees in a 3-top-of-rack(ToR)CBOSSnetwork prototype. We rely on an integrated silicon photonics (SiP) wavelength dropper, a fast-tunable laser, and custom SDN-based controller.

Tunable dual-wavelength fiber laser with unique gain system based on in-fiber acousto-optic Mach-Zehnder interferometer.

A fast tunable dual-wavelength laser based on in-fiber acousto-optic Mach-Zehnder interferometer (AO-MZI) with new fabrication process is proposed. Not only could the center wavelength of the output laser be optimized with enhanced tuning range about 30 nm by tuning the polarization and the driving frequency of the radio frequency (RF) signal accordingly, but also the spectral spacing between the two output wavelengths could be tuned from ~0 nm to 2.65 nm by controlling the power of the RF signal. The tuning mechanism was also discussed.

Fast Reconfigurable SOA-Based Wavelength Conversion of Advanced Modulation Format Data

We theoretically analyze the phase noise transfer issue between the pump and the wavelength-converted idler for a nondegenerate four-wave mixing (FWM) scheme, as well as study the vector theory in nonlinear semiconductor optical amplifiers (SOAs), in order to design a polarization-insensitive wavelength conversion system employing dual co-polarized pumps. A tunable sampled grating distributed Bragg reflector (SG-DBR) pump laser has been utilized to enable fast wavelength conversion in the sub-microsecond timescale. By using the detailed characterization of the SGDBR laser, we discuss the phase noise performance of the SGDBR laser. Finally, we present a reconfigurable SOA-based all-optical wavelength converter using the fast switching SGDBR tunable laser as one of the pump sources and experimentally study the wavelength conversion of the single polarization quadrature phase shift keying (QPSK) and polarization multiplexed (Pol-Mux) QPSK signals at 12.5-Gbaud. A wide tuning range (&gt;10 nm) and less than 50 ns and 160 ns reconfiguration time have been achieved for the wavelength conversion system for QPSK and PM-QPSK signals, respectively. The performance under the switching environment after the required reconfiguration time is the same as the static case when the wavelengths are fixed.

Software-defined control-plane for wavelength selective unicast and multicast of optical data in a silicon photonic platform.

We demonstrate a programmable control-plane based on field programmable gate array (FPGA) with a power-efficient algorithm for optical unicast, multicast, and broadcast functionalities in a silicon photonic platform. The platform includes a silicon photonic 1×8 microring array chip which in conjunction with a fast tunable laser over the C-band is capable of delivering software controlled wavelength selective functionality on top of spatial switching. We characterize the thermo-optic response of microring resonators and extract key parameters necessary for the development of the control-plane. The performance of the proposed architecture is tested with 10 Gb/s on-off keying (OOK) optical data and error-free operation is verified for various wavelength and spatial switching scenarios. Lastly, we evaluate electrical power and energy consumption required to reconfigure the silicon photonic device for all possible wavelength operations and output ports combinations and show that unicast, multicast of two, three, four, five, six, seven, and broadcast functions are achieved with energy overheads of 0.02, 0.07, 0.18, 0.49, 0.76, 1.01, 1.3, and 1.55 pJ/bit, respectively.

Autonomous Parametric Tunable Dispersion Compensation for Dynamic Optical Switching

We demonstrate dynamic parametric optical dispersion compensation in dynamic optical path networks (DOPNs). A fully automatic parametric tunable dispersion compensator (P-TDC) based on four-wave mixing process is developed with a fast tunable distributed amplification chirped sampled grating distributed reflector laser, a field-programmable gate array (FPGA) pump controller, and a fast dispersion monitor based on spectral shearing interferometer. The dispersion monitor detects a change in the dispersion of a path, and the monitoring signal is fed forward to the FPGA controller. The fast tunable laser sets its wavelength accordingly for the dispersion compensation through parametric process. A response time of <17 ms is demonstrated in a testbed of DOPN. The autonomous P-TDC has a potential response of submillisecond.

Fast Laser Spectroscopy: Dynamical Absorption Line

This paper presents analysis of the problems and principles of design of the remote, fast, and precise spectroscopic sensor, operating from the robotic platform. The typical errors of gas concentration measurement have been analyzed. It has been shown that in case of fast tunable laser spectroscopy (a sample registration time – 100ns or less) the line shape is, in principle, unrepeatable, asymmetric, and chaotically modulated at each new scan. The final composite line profile is sharper at the top as compared with a Lorentzian one and wider near the bottom. Three reasons for such specific line shape formation were considered: 1) The gas absorption line shape has been simulated by the summation of Lorentzian lines of different linewidth. The Maxwellian distribution of the molecular speeds has been used to find the molecular collisional energy distribution and related linewidths with taking into account probable number of molecules with specific impact energy; 2) Appearance of the spectral satellites when the absorption process is suddenly interrupted; 3) Spectral presentation of the collision correlation function that is modulated by massive collisions at free-flight termination. To calculate the gas concentration properly the data received from the independent sensors of pressure, temperature and humidity have been used.

Characterization of time-resolved laser differential phase using 3D complementary cumulative distribution functions

An experimental method for characterizing the time-resolved phase noise of a fast switching tunable laser is discussed. The method experimentally determines a complementary cumulative distribution function of the laser's differential phase as a function of time after a switching event. A time resolved bit error rate of differential quadrature phase shift keying formatted data, calculated using the phase noise measurements, was fitted to an experimental time-resolved bit error rate measurement using a field programmable gate array, finding a good agreement between the time-resolved bit error rates.

Dynamic linewidth measurement technique using digital intradyne coherent receivers

The phase noise characteristics and laser stabilization time of a tunable laser under both static and fast switching operation is characterized using a dynamic linewidth measurement technique which employs a digital intradyne coherent receiver. The measurement technique utilizes a time domain frequency estimator to characterize the laser phase noise and also analyses the separate noise contributions to the overall laser linewidth. The performance of the measurement technique is validated using a phase noise emulator and a low linewidth (10 kHz) external cavity laser. The dynamic stabilization time, in terms of instantaneous frequency and linewidth, of a fast switching tunable DSDBR laser is subsequently investigated and we demonstrate that a minimum linewidth for a DSDBR laser can be realized within 50 ns of a wavelength switching event in a 5-channel 50 GHz spaced WDM system.

Modulated Grating Y-Structure Tunable Laser for $\lambda$-Routed Networks and Optical Access

A fast tunable laser based on a modulated grating Y-structure (MG-Y) is demonstrated in direct burst-mode modulation at 2.5 Gb/s. Two transmission scenarios have been evaluated, and a characterization of its wavelength tuning performances in terms of wavelength switching rate and interference has been carried out. The minimum wavelength switching time was found to be 400 ps, and an optical loss budget of 26.7 dB is compatible for the use in optical transmission networks, covering distances up to 50 km while transmitting bursts at alternating wavelengths. Finally, an application in passive optical access networks allowing direct communication between the user terminals without traffic aggregation, and more important, without electrical-optical-electrical conversion or protocol-dependent termination at the premises of the service operator is presented. First results show its feasibility in hybrid wavelength division multiplexing/time division multiplexing networks that give service up to 64 users per tree.

Wavelength-reuse in optical time-slotted networks

An all-optical approach to achieve finer bandwidth granularity is to time division multiplex low capacity circuits on each wavelength channel and switch time–wavelength slots optically within the network. One such time-slotted network proposed in the literature is the Time Domain Wavelength Interleaved Network (TWIN), which eliminates slot switching within the network by using a non-reconfigurable core and an intelligent edge utilizing a fast tunable laser to emulate fast switching. In contrast to the TWIN, an optical time-slotted network which incorporates slot-switching within the network is the Time Wavelength Switched Network (TWSN), wherein the Time Wavelength Space Routers (TWSRs) are configured to change their routing pattern on a time-slot basis. The TWIN network assigns a unique wavelength to each node in the network and thus requires a total of W = N wavelengths for an N -node network. We call such a TWIN network as an unconstrained TWIN network. In this paper, we first provide integer linear programs and heuristic algorithms to solve the scheduling problem for a static traffic matrix (of connections) for both, the unconstrained TWIN and the TWSN networks and also compare their performances under a dynamic traffic scenario. To address the problem of scalability of the unconstrained TWIN network, we propose to design a wavelength-constrained (i.e., W < N ) TWIN network with no switching (TWIN-NS) by using a multicasting strategy. We also propose a variant of the TWIN network which possesses switching capabilities only at the edge nodes (TWIN-ES). Overall, this paper compares both versions of the TWIN networks to the TWSN network and investigates the benefits of having a reconfigurable core as opposed to a non-reconfigurable one.