Tunable Wavelength Conversion Research Articles

Highly tunable broadband coherent wavelength conversion with a fiber-based optomechanical system

Modern information networks are built on hybrid systems working at disparate optical wavelengths. Coherent interconnects for converting photons between different wavelengths are highly desired. Although coherent interconnects have conventionally been realized with nonlinear optical effects, those systems require demanding experimental conditions, such as phase matching and/or cavity enhancement, which not only bring difficulties in experimental implementation but also set a narrow tuning bandwidth (typically in the MHz to GHz range as determined by the cavity linewidth). Here, we propose and experimentally demonstrate coherent information transfer between two orthogonally propagating light beams of disparate wavelengths in a fiber-based optomechanical system, which does not require phase matching or cavity enhancement of the pump beam. The coherent process is demonstrated by interference phenomena similar to optomechanically induced transparency and absorption. Our scheme not only significantly simplifies the experimental implementation of coherent wavelength conversion but also extends the tuning bandwidth to that of an optical fiber (tens of THz), which will enable a broad range of coherent-optics-based applications, such as optical sensing, spectroscopy, and communication.

All-optical wavelength conversion of a 92-Gb/s 16-QAM signal within the C-band in a single thin-film PPLN waveguide.

Tunable all-optical wavelength conversion (AOWC) within 151 nm bandwidth is demonstrated in a thin-film periodically poled lithium niobate (PPLN) waveguide, which utilizes the cascaded second-harmonic generation and difference-frequency generation (cSHG/DFG) process. Also, in the same waveguide, AOWC of a 92-Gb/s 16-ary quadrature amplitude modulated (16-QAM) signal within the C-band is successfully achieved. For Bit-error ratio (BER) measurements, we obtain a negligible optical signal-to-noise ratio (OSNR) penalty (<0.2 dB) for the converted idler wave at a BER of 1e-3.

AlGaAs Nonlinear Integrated Photonics.

Practical applications implementing integrated photonic circuits can benefit from nonlinear optical functionalities such as wavelength conversion, all-optical signal processing, and frequency-comb generation, among others. Numerous nonlinear waveguide platforms have been explored for these roles; the group of materials capable of combining both passive and active functionalities monolithically on the same chip is III–V semiconductors. AlGaAs is the most studied III–V nonlinear waveguide platform to date; it exhibits both second- and third-order optical nonlinearity and can be used for a wide range of integrated nonlinear photonic devices. In this review, we conduct an extensive overview of various AlGaAs nonlinear waveguide platforms and geometries, their nonlinear optical performances, as well as the measured values and wavelength dependencies of their effective nonlinear coefficients. Furthermore, we highlight the state-of-the-art achievements in the field, among which are efficient tunable wavelength converters, on-chip frequency-comb generation, and ultra-broadband on-chip supercontinuum generation. Moreover, we overview the applications in development where AlGaAs nonlinear functional devices aspire to be the game-changers. Among such applications, there is all-optical signal processing in optical communication networks and integrated quantum photonic circuits.

Frequency conversions of nine peaks based on dispersive waves and solitons in a tellurite microstructured optical fiber.

We demonstrate the generation of broadband dispersive waves (DWs) and solitons in an 80-cm tellurite microstructured optical fiber (TMOF) designed and fabricated with 78TeO2-5ZnO-12LiCO3-5Bi2O3 (TZLB) glass. A 1810-nm femtosecond laser is used as the pump source with an average pump power ranging from 33 mW to 175 mW, where the tunable frequency range is 211.1 THz, which corresponds to the tunable wavelength range of 1742.9 nm. At 175 mW, the trapped multiple DWs are located at 923.8 nm, 1039.2 nm, 1121.6 nm, and 1204.6 nm and the multiple solitons are located at 2666.7 nm, 2426.1 nm, 2165.9 nm, 1952.7 nm, and 1842.1 nm. The experimentally obtained maximum DW conversion efficiency is 14%, and the maximum soliton conversion efficiency is 43%. The experimental and theoretical results of pulse evolution in the TMOF agree very well. To the best of our knowledge, this is the first time that nine peaks of frequency conversions have been realized simultaneously in non-silicon fibers. The exceptionally high nonlinearity and broadband-tunable characteristics of the proposed TMOF are promising components for the development of compact and highly efficient tunable mid-infrared fiber lasers, wavelength converters, and time-frequency metrology.

Tunable Terahertz Wavelength Conversion Based on Optofluidic Infiltrated Rib Silicon Waveguides

Terahertz (THz) sources have attracted special attention for various applications. Compared to the standard silica-based optical fibers, silicon waveguides have more advantages such as higher refractive index and lower absorption loss over the THz region. In this paper, for the first time, a rib silicon waveguide based on the photonic crystal (PC) idea is designed and by using the scalar modulation instability (SMI) phenomenon, tunable wavelength conversion for THz wave generation is simulated. By changing the structural parameters such as the air-hole diameter of the PC and infiltration of optical fluids into the air holes, linear and nonlinear characteristics of the waveguide are controlled and hence the generated THz radiation is considered as a tunable source. Simulation presents that the maximum converted wavelength, 326.17 μm, is obtained when the air-hole diameter is set at d = 0.86 μm and the pump wavelength is in the normal dispersion regime. Also, we have infiltrated optical fluids into PC air holes in order to change the dispersion properties of the waveguide while keeping the geometrical parameters unchanged. This led to converted wavelengths of 70.5, 76.8 and 107.5 μm, all located in the THz region. The loss of this waveguide is less than 0.8\( \raisebox{1ex}{$ dB$}\!\left/ \!\raisebox{-1ex}{$ cm$}\right. \), which is less than that of previously reported in similar silicon waveguides.

Single‐beam dual‐color alternate‐pathway two‐photon spectroscopy: Toward an optical toolbox for redox biology

AbstractWe demonstrate a versatile single‐laser platform for single‐beam dual‐color two‐photon spectroscopy that combines a short‐pulse laser source with a tunable broadband wavelength converter based on a highly nonlinear photonic‐crystal fiber (PCF). We show that the short‐pulse PCF output can be tailored, via dispersion and nonlinearity management, to deliver a broadband optical driver whose spectral structure is ideally suited for a single‐beam two‐photon absorption (2PA) spectroscopy of the next‐generation genetically encodable fluorescent‐protein (FP) sensors of pH and redox‐responsive contrast agents. As a promising spectroscopic resource for redox biology, the short‐pulse PCF output can be finely sculpted to alternately drive an FP system via a one of its two 2PA‐allowed quantum pathways, yielding a high‐contrast fluorescence readout for a highly sensitive detection of redox reactions and signaling, pH sensing, and oxidative‐stress diagnosis.

Solitons based optical packet switch analysis

Abstract Due to the evolution of data centric applications demand for high speed data transfer and more bandwidth is increasing continuously. The unavailability of components like tunable wavelength converters (TWCs) restrict the transfer of parallel information using wavelength division multiplexing (WDM), therefore in the present scenario optical orthogonal frequency division multiplexing can be used. Moreover in optical communication narrow Gaussian pulses are transmitted, which spread with distance and leads to the broadening of the pulse and pulse peak power goes down and thus limits the system. In this paper a Soliton based optical communication system is proposed and its comparison with Gaussian pulse is presented and it has been found that soliton pulse has lesser bit error rate in comparison to Gaussian pulses.

Widely Tunable Near-Infrared Wavelength Conversion Based on Central and Off-Central Multiperiod Grating Pumped by a Compact Fiber Laser

Tunable near-infrared sources are highly demanded due to their various applications in biomedicine, printing, barcode technology, and optical storage. In this paper, widely central phase-matching wavelength tunable and high efficiency are demonstrated in theoretically and experimentally, pumped by a compact all-polarization-maintaining (PM) 9-character cavity fiber laser operating near-infrared (785 nm) based on a multiperiod grating. The wavelength tuned at about 18.2 nm as the grating period changed 1 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> . A wide spectral tuning of 42 nm (from 776 nm to 818 nm) and high efficiency about 12.3% have been obtained. Besides, we discovered that the non-central second harmonic can also be generated from the second harmonic generation caused by strong phase mismatch, and the sum frequency generation (SFG) on account of the nonlinearity of the crystal. The result shows that the central and off-central phases match harmonics to form continuous broadband at some temperatures and grating periods, which can be widely exploited for wavelength conversion and tunable channel output.

Tunable wavelength conversion based on a nanoscale slot waveguide in communication bands

This paper introduces a new nanoscale slot waveguide using organic material, graphene, and silicon-based materials. The physical mechanism of additional biased voltage can improve the performance of graphene-related waveguide, the proposed waveguide exhibits tunable performance including effective refractive index and dispersion without changing its structure and geometric dimension, which contributes to the practical value in future complex signal processing system. Based on the waveguide, wavelength conversion based on four-wave mixing is theoretically investigated in the near-infrared region and the tunable wavelength conversion is realized. These research results will have potential in the fields of data transmission and optical communications and help researchers deeply understand the physical mechanisms and nonlinear effects about the optical pulse generation processes and signal processing.

Analysis of a PPLN-based cSFG/DFG wavelength conversion for capacities beyond 100 Gb/s

Wavelength division multiplexing-based networks suffer from blocking probability due to wavelength contention resolution. Such a problem can even be worth when the advanced coherently modulation formats such as M-array quadrature amplitude modulation is used to increase the channel capacity beyond 100 Gbit/s. This paper presents theoretical study of cascaded sum frequency generation and difference frequency generation based tunable wavelength conversion in a periodically poled lithium niobate waveguide as a trivial solution to the wavelength blocking problem when advanced signal modulation formats are considered. It is shown numerically that wavelength conversion of single channel up to 1 Tbit/s would be possible with a 3 cm long wavelength converter.

Experimental investigation of dispersive wave generation and evolution in a tellurite microstructured optical fiber

A four-hole tellurite microstructured optical fiber (MOF) was designed and fabricated based on TeO2–Bi2O3–ZnO–Na2O (TBZN), and the fiber loss was 0.1 dB/m@1550 nm. Based on a 3 m tellurite MOF, dispersive wave (DW) generation and evolution was experimentally investigated at the pump wavelengths of 1778 nm, 1812 nm, and 1878 nm. With the increase of the average pump power, DWs trapped by optical solitons were observed at the blue edge wavelength, but their formation became more and more difficult with the pump wavelength shifting far away from the zero-dispersion wavelength. The variation pattern of center wavelengths and peak powers of the fundamental optical solitons and DWs were investigated: the center wavelength distribution satisfied the group velocity matching; the peak power of the fundamental DW gradually exceeded that of the fundamental optical soliton with the increase of the average pump power. Furthermore, using the generalized nonlinear Schrödinger equation, simulation on the generation of DWs and optical solitons was carried out at 1778 nm, 40 mW, the result of which agreed well with the experimental observation. This investigation is instructive for DW applications in tunable laser sources, wavelength conversion, and time frequency metrology.

Analysis of AWG-Based Optical Data Center Switches

Abstract Optical packet switching (OPS) is an emerging area of research in next-generation datacenter applications. There is an exponential growth in the internet traffic due to applications such as social networking, cloud computing, video streaming, etc. Fiber optical network plays a critical role in various data center (DC) operations. Large bandwidth of the optical fiber made OPS, a promising technology for DCs. Arrayed waveguide gratings (AWGs) are used more frequently in the core of optical packet switches due to its low insertion loss and wavelength dependent routing pattern. Optical switching function can be performed by AWG if each input port is properly equipped with Tunable wavelength converters (TWCs). This paper presents analysis of four optical packet switches namely AWG and Feedback Loop Buffer based switch, AWG and Electronic Memory based switch, Petabit Optical Switch, AWG and Feedback Loop Buffer Loss Compensated based Switch. Switches are analyzed for Bit Error Rate (BER) and energy consumption. The power and noise analysis is performed for calculating the total power required for correct operation of switch and to determine the BER using physical layer analysis. Minimum power level is determined so that received bits are decoded correctly. Energy consumption per bit is also evaluated to identify architecture consuming less energy in the considered architectures.

Silicon Photonics Chip for Inter-modal Four Wave Mixing on a Broad Wavelength Range

We design, fabricate and test an integrated silicon photonics chip for inter-modal four wave mixing, whose phase-matching relays on the modal dispersions of different waveguide modes. This phase-matching technique allows for tunable and broadband wavelength conversion and generation. We demonstrate that idler and signal photons can be generated with 800 nm spectral distance in between. We measure several inter-modal combinations, with up to the third order mode involvement. We demonstrate a maximum conversion efficiency of -12.4 dB from 1468.5 nm to 1641.1 nm with a bandwidth of 11 nm. We also prove the high and broadband tunability of the generated signal by scanning the pump wavelength when the signal wavelength is fixed. All these features make the inter-modal four wave mixing a viable solution for all optical processing in the near as well as in the mid infrared and for quantum applications.

AWG-Based Nonblocking Shuffle-Exchange Networks

Optical shuffle-exchange networks (SENs) have wide application in different kinds of interconnection networks. This article proposes an approach to construct modular optical SENs, using a set of arrayed waveguide gratings (AWGs) and tunable wavelength converters (TWCs). According to the wavelength routing property of AWGs, we demonstrate for the first time that an AWG is functionally equivalent to a classical shuffle network by nature. Based on this result, we devise a systematic method to design a large-scale wavelength-division-multiplexing (WDM) shuffle network using a set of small-size AWGs associated with the same wavelength set. Combining the AWG-based WDM shuffle networks and the TWCs with small conversion range, we finally obtain an AWG-based WDM SEN, which not only is scalable in several ways, but also can achieve 100% utilization when the input wavelength channels are all busy. We also study the routing and wavelength assignment (RWA) problem of the AWG-based WDM SEN, and prove that the self-routing property and the nonblocking routing conditions of classical SENs are preserved in such AWG-based WDM SEN.

Tunable wavelength conversion based on optofluidic infiltrated photonic crystal fibers

In this paper, wavelength conversion based on optofluidic infiltration of photonic crystal fibers (PCFs) is investigated to achieve the suitable wavelength over wide tunable range. For this purpose, two designs of PCFs (the so-called PCF1 and PCF2) with appropriate dispersion properties are simulated, and wavelength conversion via four-wave mixing process for pump wavelengths in both normal and anomalous dispersion regimes is studied. By changing the refractive index [Formula: see text] of the optical fluid infiltrated into the PCF air-holes and then varying the fiber dispersion properties, the converted wavelength region can be tuned. The results show that for the pump wavelength in the normal dispersion regime, the PCF1 infiltrated with [Formula: see text] and PCF2 infiltrated with [Formula: see text] exhibit the maximum wavelength shift. Moreover, the wavelength shift is much higher than that obtained in the anomalous dispersion regime and it can be further increased by increasing the input pump power.

Characteristics of selective and tunable wavelength converters using quasi-phase matched lithium niobate waveguide devices with dual pump configuration

We report selective and tunable wavelength converters (STWCs) from an arbitrary wavelength to another arbitrary one, which employ the cascaded second-order nonlinear effect of sum frequency mixing (SFM) and difference frequency mixing (DFM) in quasi-phase matched (QPM) lithium niobate (LN) waveguide devices. Through wavelength conversion experiments using short optical pulses for the QPM-LN waveguide devices having different crystal length, we investigate bandwidth limitation of the QPM-LN-based all-optical STWCs with dual pump configuration. We show that the critical pulse width to be wavelength-converted without waveform distortion is proportional to the length of the LN crystal, and also reveal that those ratio is 1.6 ps/cm. By utilizing this critical value as a performance metric, we successfully demonstrate highly efficient selective and tunable wavelength conversion of 40-Gbit/s data signals using the SFM–DFM cascade in a QPM-LN waveguide device with an optimum crystal length of 5 cm. The 5 cm-long device can be applied to channel-by-channel wavelength conversion in 100-GHz-spaced 40-Gbit/s dense wavelength-division multiplexed systems.

PODCA: A Passive Optical Data Center Network Architecture

Optical interconnects have gained great attention recently as a promising solution offering high throughput, low latency, scalability, and reduced energy consumption compared to electrical interconnects. However, some active optical components, such as tunable wavelength converters and micro-electro-mechanical systems (MEMS) switches, suffer from high cost or slow reconfiguration times, and have been roadblocks to the realization of all-optical interconnects. In this paper, we propose three versions of a passive optical data center network architecture (PODCA), depending on the size of the network. Our key device is the arrayed waveguide grating router (AWGR), a passive device that can achieve contention resolution in the wavelength domain. In our architectures, optical signals are transmitted from fast tunable transmitters; pass through couplers, AWGRs, and demultiplexers; and are received by wide-band receivers. Our architecture can scale to over 2 million servers. Simulation results indicate that PODCA exhibits lower latency and higher throughput even at high-input loads compared with electrical data center networks such as Fat-Tree and Flattened Butterfly, and comparable performance with other optical interconnects such as DOS and Petabit, but at much lower cost and power consumption. The packet latency of PODCA in our simulation experiments is below 19 μs, and the throughput is 100%. Furthermore, we compare the power consumption and capital expenditure (CapEx) cost of PODCA with the other four architectures. Results show that PODCA can save at least 75% on power consumption and 50% on CapEx.

Optimization of wide-sense nonblocking elastic optical switches

This paper considers the optimization of wide-sense non-blocking wavelength-space-wavelength switching fabrics for elastic optical networks. Recently, wide-sense non-blocking conditions for two types of switching fabrics, named WSW1 and WSW2, have been derived and proved. In this paper, we optimize these two architectures in terms of numbers of required switching elements. Switching fabric architectures of different capacities are investigated using the full search, i.e., for each architecture and capacity, all possible configurations are checked. The results clearly present the controversy between architectures on numbers of tunable wavelength converters and their conversion range, number of input fibers and number of required bandwidth-variable wavelength selective switches. The information provided by this research can help us understand the effect of different implementation parameters, and draw more general conclusions about the parameters of optimal switching fabrics.

Synchronous optical packet switch architecture with tunable single and multi-channels wavelength converters

Abstract In this paper, we propose a bufferless synchronous optical packet switch (OPS) architecture named the Limited-range wavelength conversion with Dynamic Pump-wavelength Selection (LDPS) architecture. LDPS is equipped with a dedicated limited-range wavelength converters (LRWCs, and a shared pool of parametric wavelength converters (PWCs) with dynamic pump-wavelength selection (DPS). The adoption of hybrid conversion types in the proposed architecture aims at improving the packet loss rate (PLR) compared to conventional architecture with single conversion types, while reducing (or at least maintaining) the conversion distance ( d ) of used wavelength converters. Packet contention in the proposed architecture is resolved using the first available algorithm (FAA) and the dynamic pump-wavelength selection algorithm (DPSA). The performance of the proposed architecture is compared to two well-known conventional architectures; namely, the LRWC architecture that uses dedicated LRWCS for each input wavelength, and the DPS architecture that uses a shared pool of dynamic pump-wavelength converters (PWCs). Simulation results show that, for the same value of d , the new architecture reduces the PLR compared to the LRWC architecture by up to 40 % and 99.7 % for traffic loads, 0.5 and 1; respectively. In addition, for d = 1 , the new architecture reduces the PLR compared to the DPS architecture by up to 10 % and 99.3 % for traffic loads, 0.5 and 1; respectively.

Performance Analysis of WSS-Based ROADM With Shared-Per-Group Tunable Wavelength Converters

We propose a flexible shared-per-group (SPG) architecture for wavelength selective switch (WSS)-based reconfigurable optical add/drop multiplexers (ROADMs) to support dynamic datacenter wavelength-convertible networks. The key components of this module are grouping installed tunable wavelength converter (TWCs) and tunable filter (TFs). Using the SPG architecture, the demands that collide among different outputs will be all-optically resolved by a combination of TWCs and TFs without installing any switch matrix devices. Thus, the proposed SPG architecture may produce better blocking performance than the conventional shared-per-link, shared-per-wavelength architectures consuming lower costs. Meanwhile, analytical model is proposed to evaluate the SPG blocking probability by means of the self-constrained iteration method. Accurate results showed that SPG architecture requires the number of groups larger than the number of ports to produce the optimal blocking performance, saving 50% of TWCs under high and moderate traffic loads.