Wavelength Division Multiplexing Multiplexers Research Articles

Arrayed electro-optic modulators for novel WDM multiplexing

In this paper, a novel silicon-on-chip integrated 4 × 1 wavelength division multiplexing (WDM) multiplexer has been developed. This is the first time that the multiplexer design incorporates arrayed electro-optical modulators with crosstalk cancellation. The design utilizes two types of electro-optic modulators in each channel. The first modulator, based on 1D-PhCNBC, extracts the desired wavelengths from the WDM spectrum. The second modulator, based on coupled hybrid plasmonics, acts as a switch to eliminate crosstalk of the desired optic wavelength signal at the multiplexer output. By combining the advantages of electro-optical modulators and crosstalk cancellation techniques, we anticipate that our proposed design contributes to the advancement of WDM multiplexing technology and facilitates the implementation of efficient and compact optical communication systems. Additionally, this synergy enables enhanced performance, reduced signal interference, and improved signal quality, leading to more reliable and high-speed data transmission in optical networks. The functionality of the device is theoretically simulated using 3D-FDTD (Finite-Difference Time-Domain) method.

Next generation PON architecture using PD-NOMA employing OAM and WDM multiplexing

In this paper, we propose and experimentally demonstrate the efficacy of a next-generation passive optical network (PON) architecture for free space optical link, which utilizes power domain (PD) non-orthogonal multiple access (NOMA) along with simultaneous orbital angular momentum (OAM) mode and wavelength-division multiplexing (WDM) techniques. In this proposed architecture, many optical network units (ONUs) are accommodated by clustering them based on their power budgets and their data streams are allocated with different powers accordingly. The clustered ONUs are served with multiple OAM modes over multiple wavelengths to maintain high capacity, low latency, and increased reliability. As a proof-of-principle experimental demonstration of the proposed architecture, we have experimentally emulated two ONU clusters having a power ratio of (near:far)−3.17dB for implementing the PD-NOMA system for downlink. Each ONU cluster uses three 50 GHz spaced WDM channels, where each WDM channel carries two multiplexed OAM modes having opposite topological charge (l=±1 and ±2) values. Each cluster’s six ONUs is delivered with a 10 Gbps On-Off Keying (OOK) signal. We have demonstrated that all users can achieve a pre-forward error correction (pre-FEC) bit error rate (BER) below the 7% overhead-FEC (OH-FEC) BER limit of 3.8×10−3. We have also measured the x-talk due to WDM and mode multiplexing, and it has been revealed that the main contribution to the power penalty (relative to the no cross-talk condition) comes from OAM mode cross-talk.

Fiber optical WDM multiplexers/demultiplexers with low bending losses

Objectives. One of the topical tasks in the development of radio electronic systems for various purposes is a sharp increase in the volume and data transfer rate between the elements of the system. This problem is most successfully solved using fiber optic technology, which has no alternative to meet a number of indicators. The use of optical fibers (OF) as a physical medium made it possible to transfer large information flows over considerable distances. Increasing the capacity of communication systems is pushing manufacturers to develop new OF brands with improved optical and operational characteristics, which makes it possible to improve various optical components that use an OF as an active information transmission medium. The dual-channel single-mode wavelength division multiplexing (WDM) multiplexers/demultiplexers, which are one of spectral selective splitters types, are most widely used in fiber-optic communication systems. Among the advantages of WDM, it is worth to note the transmission of a large amount of information over one OF by the arrangement of channels at different wavelengths and the ability to transmit signals of several wavelengths simultaneously in both directions via one OF that do not interact with each other (duplex communication). During operation, WDM multiplexers can be subjected to various external influences that affect the operation and stability of the device parameters. Currently, there are no data on the effect of OF bending on the optical characteristics of WDM multiplexers. In this regard, it is important to study this dependence, which includes measuring the parameters of optical isolation and insertion loss. The purpose of the study is to work out the manufacturing technology and investigate the manufactured WDM multiplexers based on certain types of bend-resistant OF.Methods. For the formation of two-channel WDM multiplexers, the technology of fused biconical tapering was used, which makes it possible to achieve low insertion loss along with a high degree of channel isolation in the wide temperature range.Results. In the paper, the possibilities of manufacturing fiber multiplexers based on bend-resistant fiber Corning SMF-28 Ultra were discussed. The results of manufacturing and studying the experimental samples of WDM multiplexers optical characteristics were presented. It was established that the use of SMF-28 Ultra quartz fiber made it possible to significantly reduce the deviation of the channel optical isolation in the event of mechanical stresses in the multiplexers OF structure. Conclusions. The possibility of creating two-channel multiplexers with low bending losses and optical isolation up to 20–22 dB was experimentally shown. Possible mechanisms of the influence of the multiplexer fiber twisting on the optical isolation of channels were considered. The results obtained showed that when mechanical stresses in the fused structure of the multiplexer occur, the change in the optical isolation coefficient at two operating wavelengths does not exceed 1 dB.

WDM-Compatible Polarization-Diverse OAM Generator and Multiplexer in Silicon Photonics

Spatial multiplexing using orbital angular momentum (OAM) modes is an efficient means of scaling up the capacity of fiber-optic communications systems; integrated multiplexers are crucial enablers of this approach. OAM modes are circularly polarized when propagating in a fiber, however, OAM generators previously demonstrated in silicon photonics use locally linearly polarized emitters. Coupling from multiplexers to fibers in those solutions results in extra loss and complexity. Moreover, many of those solutions are based on resonator structures with strong wavelength dependence, and are thus incompatible with wavelength-division multiplexing (WDM). We experimentally demonstrate on-chip generation and multiplexing of OAM modes using an array of circularly polarized 2-D antennas with wide wavelength coverage. The proposed device was implemented on the standard 220-nm silicon-on-insulator platform. Optical vortex beams with OAM orders ranging from −3 to +3 in both left and right circular polarization states were generated from the same aperture across a wavelength range of 1540 to 1557 nm. This device could serve as a multiplexer or demultiplexer for up to 12 information bearing channels coupling into an OAM fiber, and is compatible with WDM multiplexing as well.

Wavelength Demultiplexer Designs Operating Over Multiple Spatial Modes of a Rectangular Waveguide

Wavelength demultiplexers are instrumental in wavelength division multiplexing (WDM) communications. In advance of space-division multiplexing (SDM) WDM communications, we investigate wavelength multiplexer/demultiplexer designs operating over multiplexed spatial modes simultaneously, when the modes are arranged along one transverse direction of a rectangular waveguide. The demultiplexer waveguides’ modes match those of rectangular core fibers, enabling simple and efficient edge-coupling. We describe the challenge of demultiplexing mode division multiplexed (MDM) channels, and suggest guided optics solutions for its implementation. We analyze the spatial–spectral interplay at output waveguide coupling due to mode dependent phase delays in arrayed waveguide grating router demultiplexer design, and offer low mode dependent loss solutions. The proposed schemes allow for efficient and compact MDM-enabled WDM multiplexing, paving the way to SDM-WDM communication networks.

WDM-compatible multimode optical switching system-on-chip

Abstract The development of optical interconnect techniques greatly expands the communication bandwidth and decreases the power consumption at the same time. It provides a prospective solution for both intra-chip and inter-chip links. Herein reported is an integrated wavelength-division multiplexing (WDM)-compatible multimode optical switching system-on-chip (SoC) for large-capacity optical switching among processors. The interfaces for the input and output of the processor signals are electrical, and the on-chip data transmission and switching process are optical. It includes silicon-based microring optical modulator arrays, mode multiplexers/de-multiplexers, optical switches, microring wavelength de-multiplexers and germanium-silicon high-speed photodetectors. By introducing external multi-wavelength laser sources, the SoC achieved the function of on-chip WDM and mode-division multiplexing (MDM) hybrid-signal data transmission and switching on a standard silicon photonics platform. As a proof of concept, signals with a 25 Gbps data rate are implemented on each microring modulator of the fabricated SoC. We illustrated 25 × 3 × 2 Gbps on-chip data throughput with two-by-two multimode switching functionality through implementing three wavelength-channels and two mode-channel hybrid-multiplexed signals for each multimode transmission waveguide. The architecture of the SoC is flexible to scale, both for the number of supported processors and the data throughput. The demonstration paves the way to a large-capacity multimode optical switching SoC.

Bridged Coupler and Oval Mode Converter Based Silicon Mode Division (De)Multiplexer and Terabit WDM-MDM System Demonstration

We propose a novel structure of a mode (de)multiplexer that realizes an on-chip (de)multiplexing function in a two-step process consisting of a bridged coupler and an oval mode converter. According to the two-step principle, we design and fabricate a three-mode (TE0, TE2, and TE4) (de)multiplexer with the standard silicon-on-isolator (SOI) technology. The measured crosstalk of the device is lower than −22.0 dB, −19.0 dB, and −16.0 dB for TE0, TE2, and TE4 modes, respectively, for wavelengths ranging from 1525 to 1585 nm. The device is tested in both single-wavelength and wavelength-division multiplexing (WDM) systems with 128 Gb/s (32 Gbaud) 16-ary quadrature amplitude modulation signals. We experimentally demonstrate 96-channel ( ${\text{32}}-{\text{wavelength}}\times {\text{3}}-{\text{mode}}$ ) on-chip WDM and mode-division multiplexing (MDM) transmission. Considering a single lane bit rate of 128 Gb/s, an on-chip data capacity of ∼10 Tb/s is achieved. To our best knowledge, this paper is the first demonstration of a Terabit on-chip WDM-MDM system that shows ultrahigh bandwidth communication on a single silicon chip.

Electro-optic switches based on space switching of multiplexed WDM signals: Blocking vs non-blocking design trade-offs

Short distance optical interconnects are a promising solution for tackling the bandwidth and low energy consumption requirements of next generation Data Centers (DC) and High Performance Computing (HPC) systems. The realization of optical switching should offer scalability, allowing the interconnection of multiple racks and/or servers/compute nodes, and quick reconfiguration times. To this end, fast small-radix MicroRing Resonator (MRR)- and Mach-Zehnder Interferometer (MZI)-based space switching devices, capable of supporting multiple optical signals multiplexed through Wavelength Division Multiplexing (WDM) have been reported. Using such devices as building blocks we evaluate the performance of a number of simple electro-optic switch architectures based on successive wavelength selection, WDM multiplexing and space switching, attempting to achieve scalable switching fabrics with good throughput performance on average using little additional hardware and few switching stages, thus lower total insertion losses as well as lower power consumption. The price paid for such architectural simplicity is that it introduces additional constraints on the feasible permutation matrices of such switching fabrics, affecting performance for some traffic patterns. We discuss the trade-offs between performance and hardware requirements and based, on our findings, we propose alternative architectures that overcome these limitations.

Scaling Trends for Picojoule-per-Bit WDM Photonic Interconnects in CMOS SOI and FinFET Processes

This paper presents a link analysis for optical interconnects based on CMOS scaling toward FinFET devices. An on-chip wavelength division multiplexing (WDM) link is modeled assuming silicon photonic ring modulators, WDM multiplexers and demultiplexers, and photodetectors. A high-speed CMOS transceiver is designed and evaluated using 28-nm FD-SOI and 14-nm FinFET processes. Compared to 28-nm FD-SOI, the 14-nm FinFET offers higher intrinsic gain and allows for 50% higher transconductance per drain current suggesting more energy-efficient circuit design. Cosimulation of the photonic and electronic devices demonstrates an optimum energy efficiency of $\sim 2\, \text{pJ/b}$ at $25\, \text{Gb/s}$ for a bit-error rate of $10^{-12}$ including laser and ring tuning power.

A silicon photonic wavelength division multiplex system for high-speed data transmission in detector instrumentation

We propose a new silicon photonics-based optical transmission system utilizing wavelength division multiplexing (WDM) . This technology has the possibility of reading out all raw data from a detector even without massive local data reduction. The transmitter in the detector volume consists of multiple integrated Mach-Zehnder modulators monolithically integrated with wavelength (de-)multiplexers. The first demonstrator currently under development aims for a data rate of 160 Gbit/s per fiber, scalable to 5 Tbit/s and beyond. We report on our recently developed Echelle grating WDM multiplexers with up to 45 channels on an area of 0.5 mm2 and electro-optic modulators providing a bandwidth of 18 GHz.

Four-Channel 100-Gb/s Per Channel Discrete Multitone Modulation Using Silicon Photonic Integrated Circuits

The emerging applications for inter and intradata center communications demand low-cost and small-from-factor optical transceivers with 100G/400G capacity. Various techniques, such as wavelength-division multiplexing (WDM), multilevel pulse-amplitude modulation, and discrete multitone (DMT), are heavily investigated in this field. Among these techniques, DMT can offer 100G capacity with 10–20G optical devices using direct detection, which provides a very promising low-cost 100G/400G solution. In this paper, we report silicon photonic four-channel DMT integrated circuits, which demonstrate net channel rates of 70 and 100 Gb/s detected by integrated germanium receivers and commercial receivers, respectively. The silicon photonic chip integrates four silicon Mach–Zehnder modulators and WDM multiplexers using thermally tuned second-order microring filters. Besides the wavelength multiplexing functionality, we also demonstrate that these microrings can serve as vestigial sideband filters to enhance the transmission performance in 20–40 km ranges. These demonstrations indicate the promise of using low-cost and high-integrated silicon photonic circuits in high capacity 100G/400G applications.

Radiation-resistant WDM optical link for thermonuclear fusion reactor instrumentation

The future International Thermonuclear Experi- mental Reactor (ITER) is a complex installation that will require permanent monitoring and frequent maintenance operations. The high-gamma dose rates, the high neutron fluence, and other radiological hazards call for the use of remote-handled equipment. The management of heavy umbilicals connecting the control systems with the remote tools is therefore a key issue. Multiplexing signals can relieve the cable-handling difficulties. In this respect, the intrinsic wavelength division multiplexing (WDM) capabilities of fiber-optic technology make it a very promising candidate for integration in ITER instrumentation links. However, the radiation hardness of a complete WDM optical link still needs to be assessed. In this paper, as a first step toward the development of a rad-hard WDM optical link, we report on irradiations of different parts of a typical WDM optical link. We present our irradiation results on COTS fiber-optic devices, including WDM single-mode couplers, which remain operational up to MGy dose levels while the channel drift observed in narrow-band couplers compromises their use in WDM multiplexers. The intrinsic wavelength encoding of fiber Bragg grating (FBG) sensors makes them ideal candidates for WDM fiber-optic sensor networks. Therefore, we also investigated the -radiation response of FBGs written in germanosilicate fibers. We irradiated such sensors up to MGy dose levels. At a total dose of 0.1 MGy, saturation of the radiation-induced Bragg peak shift has been observed, evidencing the potential radiation hardness of FBG-based devices in highly radioactive environments. To illustrate wavelength multiplexing in sensing, we discuss our preliminary results on a new multicomponent force sensor design based on eight multiplexed FBG sensors intended for use at the end effector wrist of remote-controlled robots. Finally, we present the in-reactor irradiation results of standard Corning Ge-doped fiber up to GGy dose levels. Index Terms—Fiber Bragg grating (FBG) sensor, gamma radia- tion, International Thermonuclear Experimental Reactor (ITER), nuclear robotics, optical fiber sensor, radiation effects, wavelength division multiplexing (WDM).