Optical Switch Module Research Articles

Mode-selective switch on silica-based PLC platform

Optical mode switch is a crucial component for the mode-division multiplexing (MDM) system. In this paper, we demonstrate a thermo-optical (TO) mode-selective switch on silica-based planar lightwave circuit (PLC) platform. The 2 × 1 thermo-optical (TO) mode-selective switch based on Mach–Zehnder interferometer consists of an adiabatic coupler and a symmetric Y-branch. The input optical mode E00 (E10) is converted to E10 (E00) mode while the light is coupled from different input ports by changing the working state of heater. With 2% index-contrast, a compact mode switch on silica-based PLC platform is fabricated. According to experimental results, the fabricated mode-selective switch shows an insertion loss lower than 5 dB and a mode extinction ratio higher than 24 dB for two modes at 1550 nm. The crosstalk is lower than −10.54 dB from 1500 nm to 1600 nm. The power consumption for two modes are 433.24 mW and 440.15 mW, respectively. The rise time and fall time of the switch are 560.9μs and 794.8μs.

High-Speed Optical Mode Switch in Lithium Niobate on Insulator

Mode-division-multiplexing technology is highly attractive to increase the capacity of optical interconnects. Various multimode operations have been investigated, among which optical mode switches provide one of the most important functions in mode-division-multiplexing systems. However, current optical mode switches have a non-negligible switching time, which can lead to an undesired cumulative delay in the optical network. In this contribution, we propose and experimentally demonstrate an optical mode switch using a three-waveguide-coupling structure in the lithium niobate on insulator platform. The demonstrated optical mode switch has an insertion loss of 4.3 dB, an extinction ratio of 17.1 dB, and a switching time of below 28 ps. This work paves the way for future chip-scale high-speed mode-division-multiplexing systems.

Research and Simulation of OCDM Switch Layer Based on 2D WDM-Optical Code Switching Structure

Optical Communication is widely used in military and civilian backbone network communication, but due to the limitation of “electronic bottleneck”, the ability of network nodes to process information and optical layer data transmission capacity is seriously mismatched, which directly causes optical cross connectors in optical nodes. The number of ports carried has skyrocketed. In order to improve the processing speed of network nodes, this paper studies the four-layer multi-granularity switching system of optical fiber, wavelength band, wavelength, and optical code, and finally builds a complete OCDMA system through simulation software, simulates multi-user simulation, and successfully realizes The encoding and decoding process is analyzed, and the performance simulation and analysis of the core switching module of the four-layer multi-layer optical switching system-OCDM switching module are carried out, and the feasibility and superiority of the selected system are verified.

Ultra-compact and low loss silicon-photonic rearrangeable non-blocking perfect shuffle-exchange network

The perfect shuffle-exchange network (PSEN) is a widely used optical network-on-chip topology. In this study, we designed a kind of rearrangeable and ultra-compact PSEN, which contains three ultra-compact components: left perfect shuffle, left inverse perfect shuffle, and 2 × 2 optical switch modules. They were then interconnected into a non-blocking 8 × 8 PSEN. The size of the entire optical PSEN module reaches only 8 µm × 87.6 µm ≈ 700 µm2, which is approximately 1000 times smaller than existing optical network-on-chip (ONoC) architectures (usual mm2 level). When signals with different wavelengths are input into different channels, the highest insertion loss in the valuable C-band is − 1.1 dB, its lowest value is − 0.7 dB, the maximum insertion loss fluctuation is only 0.4 dB, and the average crosstalk is maintained at approximately − 28 dB. This PSEN could have wide applications in nanophotonics computation and nanophotonics networks.

Topological optomechanical amplifier in synthetic PT $\mathcal{PT}$ -symmetry

Abstract We propose how to achieve synthetic PT $\mathcal{PT}$ symmetry in optomechanics without using any active medium. We find that harnessing the Stokes process in such a system can lead to the emergence of exceptional point (EP), i.e., the coalescing of both the eigenvalues and the eigenvectors of the system. By encircling the EP, both nonreciprocal optical amplification and chiral mode switching can be achieved. As a result, our synthetic PT $\mathcal{PT}$ -symmetric optomechanics works as a topological optomechanical amplifier. This provides a surprisingly simplified route to realize PT $\mathcal{PT}$ -symmetric optomechanics, indicating that a wide range of EP devices can be created and utilized for various applications such as topological optical engineering and nanomechanical processing or sensing.

Ultra-Broadband Polymer 1 × 2 Thermo-Optic Mode Switch

Optical mode switch is a key device for reconfigurable mode-division-multiplexing (MDM) technique. Here, an ultra-broadband 1×2 mode switch based on cascaded Mach-Zehnder interferometer and asymmetric Y-branch is proposed. The input E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">00</sub> or E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> mode will be converted to E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">00</sub> mode and switched between two output ports by changing the working state of electrode. When E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">00</sub> mode is launched, the measured insertion loss of fabricated switch is 3.3 dB (off-state)/3.4 dB (on-state), and corresponding crosstalk is -18.8 dB (off-state)/-16.1 dB (on-state) at 1550 nm, respectively. Due to the adoption of polymer with high thermo-optic coefficient as the waveguide material, the measured switching power is 10.3 mW. The captured far-field output mode patterns prove the wavelength independence of proposed mode switch within the range from 1500 to 1630 nm. This broadband operation mode switch has potentials in wavelength-division-multiplexing & MDM complex systems, as well as cost-effective low-end switching applications.

Highly Reliable Metro-Access Network Based on a Dual-Fiber Ring Architecture and Optimized Protection Mechanisms

Network reliability is very important for the next generation of optical networks. In this paper, a highly reliable protection mechanism, which integrates the approaches of optical protection and microwave protection, is proposed for metro-access optical networks based on the wavelength division multiplexing (WDM) technique. By designing a scheme for the convergence of optical and wireless access and cooperating with designed remote nodes (RNs), not only can access for both wired and wireless service be provided simultaneously in each optical network unit (ONU) but also microwave protection can be realized when a failure occurs in a distribution segment. By developing a novel optical switch module (OSM) to cooperate with the dual-fiber ring structure, flexible switching can be achieved to protect against multiple types of failures in the feeder segment, including single-fiber faults, dual-fiber faults and multifiber faults. Based on the above structure, the influence of Rayleigh backscattering (RB) noise can be mitigated when the network is operating under all operating scenarios except for an inner-fiber fault. To further mitigate the influence of noise, optimization for upstream transmission performance is implemented by configuring a reflective semiconductor optical amplifier (RSOA). Furthermore, the feasibility of the overall scheme is verified through experiments and simulations under different operating conditions. The results show that the proposed mechanisms can achieve acceptable bit error rate performance and quality of service (QoS) metrics while also offering various advantages, including high reliability, large scale, and a relatively low cost.

Real-time observation of vortex mode switching in a narrow-linewidth mode-locked fiber laser

Temporal and spatial resonant modes are always possessed in physical systems with energy oscillation. In ultrafast fiber lasers, enormous progress has been made toward controlling the interactions of many longitudinal modes, which results in temporally mode-locked pulses. Recently, optical vortex beams have been extensively investigated due to their quantized orbital angular momentum, spatially donut-like intensity, and spiral phase front. In this paper, we have demonstrated the first to our knowledge observation of optical vortex mode switching and their corresponding pulse evolution dynamics in a narrow-linewidth mode-locked fiber laser. The spatial mode switching is achieved by incorporating a dual-resonant acousto-optic mode converter in the vortex mode-locked fiber laser. The vortex mode-switching dynamics have four stages, including quiet-down, relaxation oscillation, quasi mode-locking, and energy recovery prior to the stable mode-locking of another vortex mode. The evolution dynamics of the wavelength shifting during the switching process are observed via the time-stretch dispersion Fourier transform method. The spatial mode competition through optical nonlinearity induces energy fluctuation on the time scale of ultrashort pulses, which plays an essential role in the mode-switching dynamic process. The results have great implications in the study of spatial mode-locking mechanisms and ultrashort laser applications.

Multi-Channel Parallel Silicon Mode-Order Converter for Multimode On-Chip Optical Switching

Various mode-order converters are implemented in optical mode multiplexing and mode switching systems. Typically, such devices can only accomplish one mode-order conversion function. In this paper, we propose a multi-channel parallel mode-order converter based on inverse-design optimization method. By using a QR-code-like silicon structure, it can realize the mode-order conversions of multiple mode channels simultaneously in a compact footprint. As a proof of concept, we design and demonstrate a dual-channel silicon mode-order converter, which converts TE0 mode to TE2 mode, and TE1 mode to TE3 mode. It has a footprint of 4 μm×3 μm. Simulation results show that the insertion losses for the two mode-order conversion process are 0.8–1.0 dB and 0.9–1.2 dB, and have good tolerance to temperature variations. The inter-mode cross-talk is lower than −19.9 dB and −17.4 dB. Experimental results show that its range of insertion losses for the two process fluctuate within 2.0–3.6 dB and 1.5–5.1 dB in the wavelength range of 1525–1565 nm. The inter-mode cross-talk is lower than −10.7 dB and −13.1 dB, respectively.

Modular Optical Cross-Connects (OXCs) for Large-Scale Optical Networks

Due to the explosive growth of traffic demands, large-scale optical cross-connects (OXCs) are highly desired in next-generation optical networks. However, the scalability of classical OXCs is not good in terms of the size of optical switching modules and cabling complexity to meet application requirement. To address this issue, this letter proposes a two-phase approach to construct modular large-scale OXCs, using a set of small-size OXC modules. We first decompose each optical space switch (OS) in a classical OXC to a Clos network and then merge the corresponding links and decomposed optical switching modules of different Clos networks to form small-size OXC modules, which finally yields a modular OXC. We show that the proposed modular OXC has good scalability and acceptable physical-layer performance.

On-chip broadband silicon thermo-optic 2☓2 four-mode optical switch for optical space and local mode switching.

We present a silicon thermo-optic 2☓2 four-mode optical switch optimized for optical space switching plus local optical mode switching. Four asymmetric directional couplers are utilized for mode multiplexing and de-multiplexing. Sixteen 2☓2 single-mode optical switches based on balanced thermally tunable Mach-Zehnder interferometers are exploited for switching function. The measured insertion losses are 8.0~12.2 dB and the optical signal-to-noise ratios are larger than 11.2 dB in the wavelength range of 1525~1565 nm. The optical links in "all-bar" and "all-cross" states exhibit less than 2.0 dB and 1.4 dB power penalties respectively below 10-9 bit error rates for 40 Gbps data transmission.

General architectures for on-chip optical space and mode switching

The optical switches for single-mode operation cannot be directly utilized in optical communication and interconnect systems adopting mode-division multiplexing. In this paper, three general architectures for on-chip optical space and mode switching are proposed, which are optimized for optical space switching, optical space switching plus local optical mode switching, and global optical mode switching, respectively. A silicon thermo-optic 2×2 four-mode optical switch is demonstrated. The minimum and maximum optical link insertion losses are 16.0 and 20.9 dB (including ∼6 dB coupling loss), respectively, in the wavelength range of 1525–1565 nm, while the optical signal-to-noise ratios of the optical links are larger than 15.3 dB. The optical power penalty at a bit error rate of 10−9 varies from 1.0 to 5.6 dB for 40 Gbps data transmission through different optical links. This work provides a systematic solution to on-chip information switching for different physical and mode channels.

All-fiber optical mode switching based on cascaded mode selective couplers for short-reach MDM networks

We propose and experimentally demonstrate an all-fiber optical mode switching structure supporting independent switching, exchanging, adding, and dropping functionalities in which each mode can be switched individually. The mode switching structure consists of cascaded mode selective couplers (MSCs) capable of exciting and selecting specific higher order modes in few-mode fibers with high efficiency and one multiport optical switch routing the independent spatial modes to their destinations. The data carried on three different spatial modes can be switched, exchanged, added, and dropped through this all-fiber structure. For this experimental demonstration, optical on-off-keying (OOK) signals at 10-Gb/s carried on three spatial modes are successfully processed with open and clear eye diagrams. The mode switch exhibits power penalties of less than 3.1 dB after through operation, less than 2.7 dB after exchange operation, less than 2.8 dB after switching operation, and less than 1.6 dB after mode adding and dropping operations at the bit-error rate (BER) of 10−3, while all three channels carried on three spatial modes are simultaneously routed. The proposed structure, compatible with current optical switching networks based on single-mode fibers, can potentially be used to expand the switching scalability in advanced and flexible short-reach mode-division multiplexing-based networks.

Optical mode switch based on multimode interference couplers

In this paper, we propose an optical mode switch based on two cascaded multimode interference (MMI) couplers. After a fundamental mode divided into two equal-power fundamental modes in the first MMI coupler, the thermo-optic effect is employed to modulate the phase of the two fundamental modes before directed to the next MMI for the purpose of mode switching. By adjusting the electric signals applied to the modulation arms, the proposed device can implement mode switching in three states: (a) one first-order and two fundamental modes simultaneously output, (b) one first-order mode output, and (c) two fundamental modes output. As a result, the simulated excess losses are −0.29 dB, −0.10 dB, and −0.63 dB, respectively.

Optical Switches Based on Silicon Photonics for ROADM Application

We demonstrate compact and low-loss 8 × 8 silicon photonic switch modules, which are applicable to transponder aggregators (TPAs) in colorless, directionless, and contentionless reconfigurable optical add-drop multiplexers. Newly designed silicon optical switch chips incorporating spot size converters with polarization insensitive and wavelength insensitive properties over C/L bands are packaged. The developed module shows about 6-dB average excess optical loss, including optical coupling loss, on all 64 optical paths with low-polarization-dependent loss and low crosstalk. Using these compact optical switch modules, we construct a TPA prototype featuring over 100-port optical switch subsystem densely mounted on one board and confirm its feasibility.

Continuous wave terahertz spectroscopy system with stably tunable beat source using optical switch

A tunable beat source has been made using an optical switch module. A stably-tunable beat source for continuous wave terahertz spectroscopy system was implemented by simply connecting 16 coaxial distributed feedback laser diodes to an optical switch. The terahertz frequency was rapidly changed without frequency drifts by changing the optical path. The continuous wave terahertz frequency was tuned from 0.05 to 0.8THz in steps of 50GHz or 0.4nm. We measured continuous wave terahertz waveforms emitted from the photomixers using the switched optical beat source. We also calculated the terahertz frequency peaks by taking fast Fourier transforms of the measured terahertz waveforms. By equipping the implemented tunable beat source with an optical switch, a continuous wave terahertz spectroscopy system was constructed and used to demonstrate the feasibility of continuous wave terahertz spectroscopy for nondestructive tests using the spectra of two type of Si wafers with different resistivity.

Electrically controlled optical-mode switch for fundamental mode and first order mode

We have proposed an optical mode switch, the principle of which is based on the partial phase shift of injected light; therefore, one important issue is to clarify the proper design criteria for the mode combiner section. We focused on the bending radius of the S-bend waveguide issue that is connected to the multi mode waveguide in the Y-junction section that acts as mode combiner. Long radius leads to undesired mode coupling before the Y-junction section, whereas a short radius causes radiation loss. Thus, we simulated this mode combiner by the beam-propagation method to obtain the proper radius. In addition, we used a trench pin structure to simplify the fabrication process into a single-step dry-etching process. As a result, we successfully fabricated an optical-mode switch with the bending radius R = 610 µm. It showed the successful electrical mode switching and the achieved mode crosstalk was approximately −10 dB for 1550 nm wavelength with the injection current of 60 mA (5.7 V).

Performance-Improved Broadcast-and-Select Optical Switch Module Based on EAM-Gate Array

Performance improvement of a broadcast-and-select (B&S) optical switch based on an electro-absorption modulator (EAM)-gate array is presented. The introduction of a novel spot-size converter (SSC) with an easy fabrication process reduced the optical coupling loss between the switch's waveguide array and input/output fibers and enhanced the optical-coupling tolerance for misalignment as the SSC properly expands the waveguide's mode field as well. In addition, the electrical crosstalk, which causes undesirable changes in the output power from different switch ports, was suppressed by the simple addition of a grounded electrode that covers the surface of passive waveguides, instead of employing a complicated regrowth process, as is usually done for electrical isolation between EAMs. A 4 $\times$ 4 B&S optical switch module has been fabricated with these improvements and has successfully exhibited low insertion loss (< 15.3 dB), little variation in insertion loss, a fast switching time (< 8 ns), low power consumption (< 3 W), and a high extinction ratio (∼50 dB).

Mode Crosstalk Evaluation Method by Using MMI Mode Filter for Optical Mode Switch

Mode Crosstalk Evaluation Method by Using MMI Mode Filter for Optical Mode Switch

Switching of whispering gallery mode in hexagonal GaN microdisk by change in condition of reflection surface

Optical microresonant mode switching in a hexagonal GaN microdisk, which acts as a whispering gallery mode (WGM) and quasi-WGM (QWGM), has been demonstrated by a change in the condition of the reflection surface under a room temperature photoluminescence (RT-PL) measurement. It has been confirmed that only the WGM in the microdisk, which uses all side walls of a microdisk as the reflection surface, was strongly affected by attaching another microdisk on a side wall. The result indicates that the WGM can be controlled independently by external factors.