Wavelength Division Multiplexing Filters Research Articles

Design and characterization of 1.3/1.55‐µm optical transceiver using straight waveguide and double‐filter photodiode

AbstractWe developed a 1.3/1.55‐µm optical transceiver module for use in asynchronous transfer mode‐passive optical network (ATM‐PON) systems, which is the global standard for optical access networks. A compact, low‐cost module was implemented by mounting the active devices such as optical devices like laser diodes (LDs) and photodiodes (PDs), and integrated circuits, and the passive devices such as optical waveguides, wavelength division multiplexing (WDM) filters, and optical fibers on the surface of a silicon (Si) bench. We adopted the simplest waveguide, the straight waveguide, to achieve the best repeatability by the SiO2 waveguide and developed a double‐filter photodiode to lessen optical crosstalk. The results achieved an output of 0 dBm from the optical fiber to 1.3 µm at 155.52 Mbit/s and a −40 dBm minimum receiver sensitivity at 1.55 µm during full‐duplex communication, and demonstrated the effectiveness of this transceiver module design. © 2002 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 85(8): 25–33, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.10028

Automated design and sensitivity analysis of wavelengh-division multiplexing filters.

An automated approach to the design of wavelength-division multiplexing (WDM) filters is based on the combination of ideas from classical design approaches with an integer optimization technique. This approach turns out to be extremely efficient from a computational point of view and makes it possible to construct a set of significantly different filter designs with nearly equivalent spectral properties. The sensitivity of WDM filters is analyzed by a computer simulation of the deposition process with turning-point optical monitoring. This analysis enables the designer to compare feasibility properties of various filter designs.

∂n/∂T measurements performed with guided waves and their application to the temperature sensitivity of wavelength-division multiplexing filters

Measurements of deltan/deltaT of thin films by the m-lines technique are presented. The importance of the substrate material is shown. An example of the wavelength shift of an optical thin-film filter with temperature is studied both theoretically and experimentally. The theoretical wavelength shift of a dense wavelength-division multiplexing filter is discussed.

Theoretical study of amplitude and phase filtering of guided waves.

The design of integrated optics filters by use of refinement software based on the Abelès thin-film computation method and the film mode matching method is studied. The results obtained with the two computation methods are compared. Good agreement is obtained provided that the fill factor of the guided mode in the component is high and that modal losses between waveguide sections are simulated by absorption with the Abelès computation method. Integrated optics devices that manage either the amplitude of guided waves such as a dense wavelength division multiplexing narrow-bandpass filter and a gain-flattening filter or the phase of guided waves such as a broadband dispersion compensator are

A new type of small size acousto-optic tunable filter with super narrow optical linewidth

The new concept of the creation of an acousto-optic tunable filter (AOTF) with super-resolution and small size is discussed. The advantage of the device is based on the use of a novel type of multi reflector beam expander that produces a highly collimated optical beam (angular spread about 100 ppm), tilted with a change in optical wavelength. The proposed AOTF, 1 cm in length, can have an optical linewidth about 0.1 nm and up to 400 tunable channels at a wavelength of 1540 nm. It can be utilized as a tunable filter for dense wavelength-division multiplexing (DWDM) in fiber optic networks and as a small-sized tunable optical spectrometer, for example, in sensors of gases, liquids and solids. The acousto-optic tunable filter can be developed by known technology developed for the creation of integrated optics and microelectronics devices.

Wavelength-division multiplexing isolation filter using concatenated chirped long period gratings

We propose the use of concatenated chirped long period gratings as an efficient wavelength-division multiplexing (WDM) isolation filter. The proposed filter not only works in the transmission mode but also has almost equispaced pass bands with high isolation at the stop bands. The filter has negligible dispersion effects in the pass band, which should make such a device suitable for use in WDM fiber optic communication links.

Multimode resonances in square-shaped optical microcavities

Square-shaped two-dimensional optical microcavities (micro-cavities) were investigated for possible applications as filters for dense wavelength-division multiplexing. Multimode cavity resonances were observed in the elastic scattering of approximately 200-microm square-shaped micro-cavities in fused silica. Based on a two-dimensional k-space representation, we accounted for the multimode spectrum by different normal modes with rays confined by total internal reflection. The cavity-mode trajectories need not be closed after each round trip. Single-mode spectra are expected from smaller square-shaped micro-cavities.

A 1.3/1.55-/spl mu/m wavelength-division multiplexing optical module using a planar lightwave circuit for full duplex operation

We developed a hybrid integrated optical module for 1.3/1.55-/spl mu/m wavelength-division multiplexing (WDM) full-duplex operation. The optical circuit was designed to suppress the optical and electrical crosstalk using a wavelength division multiplexing filter, and an optical crosstalk of -43 dB and an electrical crosstalk of -105 dB were achieved with a separation between the transmitter laser diode and the receiver photodiode of more than 9 mm. We used the optical circuit design to fabricate an optical module with a bare chip preamplifier in a package. This module exhibited a full duplex operation of 156 Mbit/s with a minimum sensitivity of -35.2 dBm at a bit error rate of 10/sup -10/.

A Bidirectional Optical Module Based on Stacked Planar Optical Circuit

In this paper, a bidirectional optical module based on a stacked planar optical circuit (SPOC) concept to perform a wavelength division multiplexing (WDM) function is described. The module consists of an optical chip which incorporates planar microlens (PML) arrays and nonpolarizing 1.31/1.55 µm WDM dielectric-multilayer filters. Module design and theoretical estimation of loss tolerance were conducted. From preliminary experiments, the feasibility of SPOC modules was confirmed. A fabricated WDM filter showed a small polarization-dependent loss (PDL) of about 0.48 dB and 0.05 dB for the wavelengths of 1.31 µm and 1.55 µm, respectively. Channel crosstalk and PDL for the SPOC module were characterized by means of discrete filter devices. For the 1.55 µm downstream (1.31 µm downstream/upstream) channel, a crosstalk as low as -40 dB (-26 dB) and a PDL less than 0.23 dB (0.53 dB) were achieved.

Bragg grating fast tunable filter for wavelength division multiplexing

A Bragg grating fast tunable filter prototype working over a linear tuning range of 45 nm with a maximum tuning speed of 21 nm/ms has been realized. The tunable filter system is based on two piezoelectric stack actuators moving a mechanical device thus compressing an apodized fiber Bragg grating. The filter allows both traction and compression and can work in transmission and in reflection. It is designed to work with a channel spacing of 100 GHz according to the ITU specifications for wavelength division multiplexing systems.

Bandpass filters for wavelength division multiplexing—modification of the spectral bandwidth

Dispersion of the phase shift upon reflection of the reflectors is used to narrow the spectral bandwidth of an all-dielectric bandpass filter for wavelength division multiplexing. The bandwidth is altered by the shifting of the order numbers of the spacer layers (of multiple half-wave optical thicknesses).

Wavelength-division multiplexing free-space optical interconnect networks for massively parallel processing systems

Wavelength-division multiplexing (WDM) techniques provide many advantages for building optical interconnect networks for massively parallel processing (MPP) systems. A design for a 1024-channel network for MPP systems based on the interconnection-cached network with vertical-cavity surface-emitting laser (VCSEL) arrays with one wavelength is described. We then show how a WDM version with four different wavelengths can increase the channel density. We also show how a WDM system can reduce the fan-in loss by a factor of 4. All the VCSEL's in each array are of the same wavelength, while different arrays use different wavelengths. We describe our experimental WDM subsystem containing four VCSEL arrays, operating at wavelengths of 843, 950, 970, and 980 nm, and three different WDM filters for multiplexing-demultiplexing. We present the operational results of the subsystem at 1 Gbit/s per channel.

An Optical Network Unit (ONU) Chip Based on Stacked Planar Optics

In this paper, an optical network unit (ONU) based on stacked planar optics is described. The ONU chip consists of planar microlens (PML) arrays and dielectric multilayered filters conveniently arranged to perform a wavelength division multiplexing (WDM) transmitter/receiver function. To avoid polarization dependence, nonpolarizing filters were designed for WDM filters, half-mirrors and mirrors. An insertion loss of less than 2.5 dB and a polarization-dependent loss (PDL) of less than 0.5 dB were obtained for the 1.3 µm port. Crosstalk was estimated to be as low as -26 dB. For the 1.55 µm port, both insertion loss and PDL of less than 0.08 dB were obtained.

All-fiber zero-insertion-loss add–drop filter for wavelength-division multiplexing

We developed and fabricated an all-fiber add-drop filter by recording a Bragg grating in the waist of an asymmetric mode converter-coupler formed by adiabatic tapering and fusing of two locally dissimilar, single-mode optical fibers. The insertion loss of the device was ~0.1 dB .A narrow spectral bandwidth (<1 nm) and a large add-drop efficiency (>90%) were also demonstrated. In addition, the filter was polarization independent.

Guiding filters for massive wavelength division multiplexing in soliton transmission

In soliton transmission, third-order dispersion of the transmission fibers tends to cause unacceptable variation in the filter strength parameter eta over the wide wavelength bands required for massive wavelength division multiplexing. We show how to vary the mirror reflectivities of etalon filters with wavelength, such that eta , in soliton units, nevertheless remains at the optimal value across the entire transmission band, and we show how to achieve the required R(lambda) accurately and reproducibly by making the etalons from gratings written in fiber.

Coupled-mode analysis of fiber-optic add–drop filters for dense wavelength-division multiplexing

We present a coupled-mode theory of fiber-optic add-drop filters, which involve directional coupling between two fibers combined with fiber Bragg gratings defined inside the coupling region. The analysis self-consistently accounts for both the directional and the reflection coupling, and the propagation constants and structure of the supermodes of the combined structure are derived. We present a detailed analysis of a filter design based on identical fibers. The calculated device parameters satisfy the requirements for dense wavelength-division multiplexing applications.

Optical-fiber filters for wavelength division multiplexing

Optical-fiber filters for wavelength division multiplexing

Optical bistable device with one sinusoidal amplitude grating

A novel type of optical bistable device (OBD) based the Abble theory is proposed, in which the modulation is realized by moving one sinusoidal amplitude grating. When the parameters of this system are chosen properly this system can be a one-channel or two-channel optical bistable device. The mathematical models which describe the optically bistability are obtained. Numerical simulations on the optical bistabilities and the stability analysis on this system for two cases are given. The two-channel OBD may work as a 1 × 2 optical switch or a stable filter for wavelength division multiplexing, and may be applied in code-division multiple access networks and optical recovery circuit.

Analysis and design for optical video transport distribution system with video on demand service

A cost-effective methods of multiplexing, transmitting, and selecting optical video signals is proposed and demonstrated by using appropriate combinations of bidirectional optical trunk-amplifier, medium-density wavelength division multiplexing (WDM) and optical space switching techniques for rapid cost-effective construction. The major factors affecting optical video transport/distribution system design are described. In particular, a tapping-type optical loop-shaped trunk section network is proposed from the viewpoint of system reliability, probability of call-loss, and "B-ISDN with analog overlay." The experimental results and design philosophy for an optical selector composed of WDM filters and space switches connected by silica-based waveguide on a chip are also discussed.