Wavelength Division Multiplexing Demultiplexer Research Articles

On-Chip Multichannel Dispersion Compensation and Wavelength Division MUX/DeMUX Using Chirped-Multimode-Grating-Assisted Counter-Directional Coupler

On-chip optical dispersion compensation and wavelength division multiplexing/demultiplexing (WDM) are highly demanded functions for optical communications. In this work, we proposed a multichannel dispersion compensation structure based on chirped multimode grating within a counter-directional coupler (CMG-CDC). Simultaneous wavelength division multiplexing and demultiplexing can be realized within a compact footprint. A device design for four-channel CMG-CDC at the C/L (1530–1565 nm) band is presented with a channel spacing of 20 nm assisted by a grooved multimode waveguide structure. The average dispersion for all channels is about −2.25 ps/nm with a channel bandwidth of about 3.1 nm. The device is highly compact and highly scalable, which makes it rather convenient for increasing the group velocity dispersion (GVD) and channel number, indicating flexible applications for versatile systems, including typically coarse wavelength division multiplexer four-lane (CWDM4) transceivers.

Active tunable WDM demultiplexer with intrinsic gain based on vectorial parametric amplification.

We report on the realization of an active tunable wavelength division multiplexing (WDM) demultiplexer based on vectorial parametric amplification in a highly nonlinear bismuth-oxide fiber. The demultiplexing of a 10 Gbits/s WDM channel is demonstrated with little power penalty. The compact device integrates wavelength conversion and filtering functions while providing parametric gain. Furthermore, the proposed scheme could be extended to perform time division multiplexing (TDM) and WDM simultaneously.

Design and performance analysis of eight channel demultiplexer using 2D photonic crystal with trapezium cavity

In this work, an eight-channel dense wavelength division multiplexing demultiplexer is designed with a 2D photonic crystal triangular lattice. The proposed demultiplexer consists of a centre bus waveguide, an isosceles trapezium resonant cavity, and an eight-circular ring cavity (CR1, CR2, CR3, CR4, CR5, CR6, CR7, and CR8). The point defect resonant cavity consists of seven rods to drop different wavelengths from eight cavities, each of eight drop waveguides. The design is very simple to realise. The finite difference time domain and plane wave expansion method methods were used to analyse the proposed design’s band structure and transmission spectrum. The resonant wavelengths are 1.5441 μm, 1.5443 μm, 1.544 49 μm, 1.5447 μm, 1.5449 μm, 1.5451 μm, 1.5453 μm, and 1.5455 μm respectively. The proposed device provides a high-quality factor, transmission efficiency, and low crosstalk. The device’s footprint is 490.0 μm2, which can be easily incorporated into photonic integrated circuits.

Silicon photonic flat-top WDM (de)multiplexer based on cascaded Mach-Zehnder interferometers for the 2 µm wavelength band.

The 2 µm wavelength band has proven to be a promising candidate for the next communication window. Wavelength-division multiplexing (WDM) transmission at 2 µm can greatly increase the capacity of optical communication systems. Here, we experimentally demonstrate a high-performance silicon photonic flat-top 8-channel WDM (de)multiplexer based on cascaded Mach-Zehnder interferometers for the 2 µm wavelength band. A three-stage-coupler scheme is utilized to provide passbands and reduce channel crosstalk, and 11 thermo-optic phase shifters have allowed active compensation of waveguide phase errors. The fabricated device shows low insertion loss (< 0.9 dB), channel crosstalk (< 20.6 dB) and 1-dB bandwidth of 2.3 nm for operating wavelength ranging from 1955nm to 1985nm. The demonstrated (de)multiplexer could potentially be used for WDM optical data communication in the 2 µm spectral band.

Cascaded AMZ triplets: a class of demultiplexers having a monitor and control scheme enabling dense WDM on Si nano-waveguide PICs with ultralow crosstalk and high spectral efficiency.

We propose a class of wavelength-division multiplexing (WDM) demultiplexers having a novel monitor and control scheme enabling dense WDM on Si nano-waveguide (NW) photonic integrated circuits (PICs), which had been impossible due to the critically small fabrication tolerance of the extremely miniaturized waveguide structure. With a computer simulation, we show our proposed demultiplexers enable crosstalk in the range of -50 to -40 dB, flat-topped spectrum for high spectral efficiency, and channel counts as large as 64. We have experimentally evaluated the validity of this type of demultiplexers by using a 4-ch WDM demultiplexer, which has shown total crosstalk of < -49 dB as a result of fully automatic control of heaters. This technology is expected to drastically shrink the size of dense WDM transceivers, paving the way for future sustainable scalability in the capacity of optical transceiver systems.

Scan-less 3D optical sensing/Lidar scheme enabled by wavelength division demultiplexing and position-to-angle conversion of a lens.

We propose a novel scheme for 3D sensing or Lidar without the need for beam scan or 2D photo-imaging. The scheme is enabled by the combination of a lens' position-to-angle conversion and the wavelength division multiplexing/demultiplexing (WDM) commonly used in optical fiber communication systems. However, unlike in a WDM system where different wavelengths carry different data channels, here lights of different wavelengths are demultiplexed into different waveguides or fibers with their exiting ends placed in the focal plane of the lens, which converts the exiting lights into beams of different angles to form a 1D or 2D beam array according to the relative position of the fiber ends with respect to the optical axis of the lens for illuminating the targets and finally sensing the light reflected from different directions. The returned signals are then demultiplexed into different photodetectors to determine the distances of the reflections in different directions. We show that the scheme has the potential to be implemented in photonics integrated circuit (PIC) for low cost production. We successfully demonstrate the scheme with the off-the-shelf discrete fiber optic components using 4 WDM channels and time-of-flight (ToF) technique for distance measurement, although hundreds wavelength channels from a photonic integrated microcomb may be used in practice. Finally, we demonstrate that the angular resolution of the beam array of different wavelengths can be improved by dithering the fiber array or the lens. We believe this new scheme provides an attractive alternative to the MEMS and optical phased array based beam scanning and can be explored further to enable low cost and high speed 3D sensing, particularly Lidar systems.

2D-Photonic Crystal based Demultiplexer for WDM Systems – A Review

Abstract Photonic crystals (PCs) have an excellent ability to confine and control the manipulation of light. PCs are periodic or aperiodic arrangement of dielectric, metallo dielectric or super conductor micro and nanostructure materials. The periodicity of refractive index distribution in one, two and three dimensions affects the propagation of electromagnetic waves inside the PC structure. As a result of periodicity, photonic band gap (PBG) exists in a specific wavelength of PC structure and reflects the beam of light through it. This is an active part to design optical devices with a specified wavelength range. The PBG of periodic and aperiodic structures is calculated by plane wave expansion method. The wavelength division multiplexing (WDM) is an emerging technology in optical field. The multiplexer and demultiplexer are playing a prominent role for transmission and reception of light signals in WDM systems. This paper investigates and enumerates the two-dimensional (2D) PC square lattice structure-based WDM demultiplexers using quasi-square ring resonator (QSRR). The periodic array of inner rods located inside the QSRR whose shapes and refractive index justify the resonant wavelength of the channels. The channels are dropped at output ports with different resonant wavelengths by altering the size and refractive index of cavity. Typically, the resonant wavelength of the channel is shifted to higher wavelength while increasing the dielectric strength of the QSRR. The dielectric strength of the QSRR is altered by varying the inner rod radius which reflects the size of the air gap. The demultiplexer is composed of bus waveguide, scatterer rod, and reflector rod whose dimensions are also responsible to enhance or alter the performance of the systems. The finite difference time domain method is utilized to analyse the functional parameters of the structure such as the resonant wavelength, transmission efficiency, Q factor, spectral width, channel spacing and crosstalk. The impact of performance parameters is investigated through different shape of inner core and refractive index of QSRR. The observed resonant wavelength of the channels (1,525–1,610 nm) of the demultiplexers is falling under WDM systems and overall size is minimized to 434.16 μm2. The average channel spacing is about 0.75 nm, spectral width is 0.76 nm, Q factor is 2,036 and crosstalk between the channels is −30 dB. The significance of the attempt is to reduce the crosstalk which is attained by grouping odd and even numbers of channels separately. Finally, four-channel demultiplexer is designed by altering the refractive index of the inner rods (i. e. inner core) linearly and the performance parameters are investigated. Then, the point-to-point network is designed to incorporate and evaluate the performance of the demultiplexer. The observed maximum travelling distance, Bit Error Rate (BER) and receiver sensitivity of the network are 85 km, 10−9 and −16 dBm, respectively. The device could be incorporated in photonic integrated circuits for dense WDM applications.

Modeling of Small Size and Low Crosstalk Dense Wavelength Division Multiplexing Demultiplexer Based on Photonic Micro Ring Resonator

Modeling of Small Size and Low Crosstalk Dense Wavelength Division Multiplexing Demultiplexer Based on Photonic Micro Ring Resonator

Photonic crystal ring resonator-based four-channel dense wavelength division multiplexing demultiplexer on silicon on insulator platform: design and analysis

A micro/nanofabrication feasible compact photonic crystal (PC) ring-resonator-based channel drop filter has been designed and analyzed for operation in C and L bands of communication window. The four-channel demultiplexer consists of ring resonators of holes in two-dimensional PC slab. The proposed assembly design of dense wavelength division multiplexing setup is shown to achieve optimal quality factor, without altering the lattice parameters or resonator size or inclusion of scattering holes. Transmission characteristics are analyzed using the three-dimensional finite-difference time-domain simulation approach. The radiation loss of the ring resonator was minimized by forced cancelation of radiation fields by fine-tuning the air holes inside the ring resonator. An average cross talk of -34 dB has been achieved between the adjacent channels maintaining an average quality factor of 5000. Demultiplexing is achieved by engineering only the air holes inside the ring, which makes it a simple and tolerant design from the fabrication perspective. Also, the device footprint of 500 mu m(2) on silicon on insulator platform makes it easy to fabricate the device using e-beam lithography technique. (C) 2018 Society of Photo-Optical Instrumentation Engineers (SPIE)

Silicon-based hybrid demultiplexer for wavelength- and mode-division multiplexing.

A silicon-based hybrid demultiplexer for wavelength-division multiplexing (WDM) and mode-division multiplexing (MDM) is proposed and demonstrated by integrating an M-channel-mode demultiplexer and N-channel WDM filters based on microring resonators (MRRs) with box-like responses. For the mode demultiplexer, the 2k-th output port is connected with the (2k+1)-th output port through the bus waveguide for the k-th MRR array, so that each MRR-based optical filter works bi-directionally and provides two drop ports. As an example, a 32-channel hybrid MDM-WDM demultiplexer is realized by integrating a 4-channel mode demultiplexer based on dual-core adiabatic tapers and two bi-directional MRR-based WDM filters with eight wavelength-channels. For the fabricated hybrid demultiplexer, the excess loss is 0.5-5dB, the intermode cross talk is -16.5 to -23.5 dB, and the cross talks between the adjacent and nonadjacent wavelength channels are about -25 dB and -35 dB, respectively.

A flexible millimeter-wave radio-over-fiber system for various transmission bit rate

In this paper, we propose a flexible scheme to generate millimeter-waves (MMWs) for millimeter-wave radio-over-fiber (MMW-RoF) system. The proposed scheme has two configurations to adapt to various transmission bit rate by slightly rearranging the allocation of the system. The main structure of the system is cascaded LiNbO3 Mach-Zehnder modulators (LiNbO3-MZMs). The first configuration is cost effective method, where we utilize a wavelength division multiplexing de-multiplexer (WDM Demux) and an optical splitter (OS) to generate two unmodulated optical signals and a modulated optical signal. Each unmodulated optical signal and the modulated signal will form an optical single sideband (OSSB) modulation and therefore we simultaneously achieve a Q-band (45GHz) and a V-band (60GHz) MMWs in the receiver. The bit-error-ratio (BER) curves show that the power penalties of 45GHz and 60GHz are 0.6dB and 1.1dB at a BER of 1×10−9 with 2.5Gb/s transmission data rate and 50km fiber transmission distances. The second configuration can accommodate high bit rate, where few optical devices is rearranged to only generate a 60GHzMMW with 40Gb/s 4 quadrature amplitude modulation orthogonal frequency division multiplexing (4-QAM OFDM) signals. The power penalty is 1.1dB at a BER of 1×10−9 with 50km fiber transmission distances. Therefore, the proposed scheme can flexibly generate either two Q&V-band MMWs (45GHz and 60GHz) for the applications of the low data-rate transmission systems or one V-band MMW (60GHz) for the applications of the high data-rate transmission systems.

Design and optimization of photonic crystal based eight channel dense wavelength division multiplexing demultiplexer using conjugate radiant neural network

In this paper, two dimensional photonic crystal, based eight-channel demultiplexer is proposed and designed for DWDM applications. The performance parameters of the demultiplexer such as transmission efficiency, channel spacing, spectral line width, Q factor, and crosstalk have been evaluated. The proposed demultiplexer comprises of bus waveguide, drop waveguide and parellogram resonant cavity (PRC). The bus waveguide transmits light to the PRC and exits through respective drop waveguide. The PRC consists of a parellogram resonator with a nano ring cavity that is used for dropping eight specific wavelength for ITU-T G 694.1 standard with 50 GHz channel spacing. The circular ring resonator is placed above the PRC wherein a resonant air hole (Cr) is positioned for desired channel selection. The channel selection is done by altering the radius of the air hole. In addition, a conjugate radiant neural network is implemented for optimizing the radii of resonant air holes to select the required channel wavelength. The proposed device is very compact and it could be considered for implementing the photonic integrated circuits.

Integration of both dense wavelength-division multiplexing and coarse wavelength-division multiplexing demultiplexer on one photonic crystal chip

An integrated model of photonic crystal (PC) demultiplexer that can be used to combine dense wavelength-division multiplexing (DWDM) and coarse wavelength-division multiplexing (CWDM) systems is first proposed. By applying the PC demultiplexer, dense channel spacing 0.8 nm and coarse channel spacing 20 nm are obtained at the same time. The transmission can be improved to nearly 90%, and the crosstalk can be decreased to less than −18 dB by enlarging the width of the bus waveguide. The total size of the device is 21×42 μm 2 . Four channels on one side of the demultiplexer can achieve DWDM in the wavelength range between 1575 and 1578 nm, and the other four channels on the other side can achieve CWDM in the wavelength range between 1490 and 1565 nm, respectively. The demonstrated demultiplexer can be applied in the future CWDM and DWDM system, and the architecture costs can be significantly reduced.

PLASMONIC-BASED DEVICES FOR OPTICAL COMMUNICATIONS

To meet the demand of delivering ever-increasing Internet traffic, optical network must response by increasing its transmission capacity. Since transmission capacity of an individual fiber is still well exceed the capacity of transmitters (TXs) and receivers (RXs), wavelength-division multiplexing (WDM), in which many TXs and RXs at the transmitting ends of a fiber are used to send and receive many signals, becomes the necessary technology for increasing the transmission capacity of each link of an optical network. This trend, however, demands for increasing density not only the TXs and RXs, but all other components at the sending and receiving ends of communications links. As the number of wavelengths in WDM configuration getting greater, the number of all these components that must be placed on one board has to increase too; hence, the density of packaging comes to micro- and even nano-scale. The TXs and RXs are produced in arrays on a chip quite similar to production of VLSI electronic circuits. At that scale, traditional optical operations used today in an optical-communications technology, such as launching light into optical fiber from TXs and directing light from optical fiber into RXs, multiplexing and demultiplexing individual channels (wavelengths), and electro-optical (E/O) and opto-electrical (O/E) conversions become problems primarily because of the diffraction limit. The problems associated with the diffraction limit are particularly acute for optical interconnects. One of the possible solutions to all these—and some other—problems could be the use of plasmonics. In the last years, the optical-communications industry shows a great interest in developing this topic, as the growing number of publications and practical results can attest. This paper consists of two parts. The first part reviews the current trends in application of plasmonics in optical communications and the second part discusses the theoretical foundation of the proposed WDM demultiplexer and offers the scheme of possible implementation of the device.

WDM DEMULTIPLEXING BY USING SURFACE PLASMON POLARITONS

The volume of telecommunications traffic keeps growing at an exponential rate. The optical-communications industry, the linchpin of modern telecommunications, in its quest of keeping up with this growth simply must increase the number of wavelengths in the wavelength-division multiplexing (WDM) configuration. The result of this increase would mean, too, that the number of transmitters and receivers that could be placed on one board would increase as well; hence, the density of their packaging would come to micro- and even nano-scale. At the receiver end, which we will consider in this paper, manufacturers are now able to fabricate an array of photodiodes (PDs) on a single wafer, reducing the size of an individual PD to hundreds of nm. The main obstacle in approaching this scale from a communications link point of view, however, is the diffraction limit. One possible solution to this problem is the use of plasmonics. This paper discusses a possible approach to using surface plasmon polaritons (SPPs) for WDM demultiplexing, presents a possible scheme to implement this approach, and offers our analysis of this scheme along with suggestions for future developments.

Non-inverted multiple wavelength converter at 40 Gbit/s using 1550 nm quantum dot SOA

Error-free and low penalty (<2.5 dB) 1×4 multiwavelength conversion at 40 Gbit/s in a 1550 nm quantum dot semiconductor optical amplifier (QD-SOA) is demonstrated. The suggested converter makes use of a simplified filtering scheme based on a standard telecom grade dense wavelength division multiplexing demultiplexer (Demux). By detuning the wavelength of the continuous-wave probes out of the Demux's passband, a non-inverted wavelength converted signal is available at each of the Demux's outputs. Albeit significant fibre-to-fibre losses of the non-packaged QD-SOA (∼10 dB), only a low penalty is reported, mainly due to the low noise at the amplifier's output, with similar performance for a single and multiple wavelength conversion operation of the setup.

Over-1000-channel ultradense WDM transmission with supercontinuum multicarrier source

In this paper, ultradense wavelength-division multiplexing (WDM) transmission technologies are discussed, and a field demonstration of over-1000-channel ultradense WDM transmission is reported. The generation of an ultradense WDM signal using a supercontinuum multicarrier source that generates more than 1000 carriers and uniform precise channel spacing of 6.25 GHz is presented. The influence of four-wave-mixing generated in the transmission fiber and the requirements placed on the WDM multiplexer and demultiplexer is described. An over-1000-channel ultradense WDM transmission experiment is reported. A 1046 /spl times/ 2.67-Gbit/s 6.25-GHz-spaced ultradense WDM signal is successfully transmitted over 126 km of field-installed fibers in the test bed of JGN II.

Packet labeling technique using electronic code-division multiple-access for WDM packet-based access networks

We propose and experimentally demonstrate the feasibility of a packet labeling technique using electronic code-division multiple-access for a wavelength-division-multiplexing (WDM) packet-based access network, whereby each wavelength is assigned a unique electronic code-based label on a radio-frequency subcarrier. Such a technique allows individual wavelength channels to be electronically identified without requiring the use of a WDM demultiplexer. We experimentally demonstrate this technique with two WDM channels each with 1.25-Gb/s payload data and 10-Mb/s header coded onto an electronic code at 160 Mb/s. The experimental results and theoretical analysis show that this technique has the potential to support large numbers of WDM channels.

Theory of light refraction at the surface of a photonic crystal

A rigorous theory is developed for light refraction by a photonic crystal (PC) with arbitrary lattice-type and surface orientation. First, the refraction of a planar wave incident upon a photonic crystal surface is analyzed. We rigorously prove the equal partition of propagating PC modes by a surface under a general condition. The concept of surface-orientation-dependent mode degeneracy has been proposed and its relationship to quasi-periodic surfaces unfolded. With modes partitioned and the degeneracy properly recognized, a subset of the solved PC modes is identified to uniquely represent all PC modes that can be excited by an incident wave. The refraction problem can thus be rigorously solved in the plane-wave formulation. Essentially, we need to solve the field in only a single cell on the surface to solve the refraction problem. We further discuss the case where a Bloch wave illuminates the surface from inside a photonic crystal, which enables us to compute the transmissions along a complete light path through a series of interfaces. In addition, the transmission of a Gaussian beam is discussed, and the insertion loss formulas are presented. Other realistic beam profiles are discussed for designing photonic crystal devices. With all these issues solved, a complete theoretical framework of the photonic crystal refraction and transmission has thus been established. The theory has been applied to design a wavelength-division multiplexing demultiplexer that exhibits lower than $3\phantom{\rule{0.3em}{0ex}}\mathrm{dB}$ loss over a $25\text{\ensuremath{-}}\mathrm{nm}$ spectrum. In examining the refraction by a quasiperiodic surface, a slight change of surface orientation is predicted to split one beam into an infinite number of beams.

Polarisation and wavelength division multiplexing at 1.55 ?m for bandwidth enhancement of multimode fibre based access networks

We demonstrate how a combination of polarisation-division multiplexing (PDM) and wavelength-division multiplexing (WDM) applied to graded index 50 mum multimode fibres (MMF) at 1.55 mum can be used to greatly increase the available optical bandwidth. A proof of principle experiment demonstrated error-free data transmission over 3km of MMF, using two 100GHz-spaced wavelengths, each carrying two 2.5Gb/s orthogonal PDM multiplexed channels, resulting in a 10Gb/s data rate. Polarisation and wavelength demultiplexing were simultaneously achieved by use of a grating based monochromator. We also practically implemented this transmission scheme in an all-fibre experiment, replacing the monochromator by a more convenient polarisation-insensitive, 200GHz ITU grid spacing 62.5 mum MMF pigtailed WDM demultiplexer. Using two polarizations each on four wavelengths (2P x 4lambda), we repeatedly achieved error-free data transmission for both circularly and linearly polarisation-wavelength-division-multiplexed channels over a MMF span of 300m, featuring a 20Gb/s data rate. Overall, we have demonstrated a major increase in the MMF bandwidth-distance product up to 30GHz-km.