This paper describes several high performance computing testbeds being developed for Ballistic Missile Defense Organization applications that are based on high speed wavelength division multiplexed (WDM) fiber optic packet network technology. By combining high speed (> 100 Gb/s per channel), low latency (< 1 us), and scalability, these WDM networks offer the possibility of creating very closely coupled meta-supercomputers for real-time theater defense applications. The testbeds consist of: (1) coarse grain architecture consisting of a few large massively parallel processor supercomputers connected by striped WDM trunks, (2) fine grain architecture consisting of clusters of workstations connected by a fast WDM packet network, and (3) a hybrid satellite/WDM fiber network for global grid. These all-optic networks are expected to enable a number of distributed teraflop applications, such as real- time image fusion, real-time radar signature analysis and modeling, very large scale simulation, and realistic synthetic scene generation. This paper describes these testbeds in more detail and their specific WDM component requirements.

The government subsidizes American small businesses to create WDM (and four zillion more technologies). The Ballistic Missile Defense Organization (BMDO) supplies a little seed capital for infant development and then a little more when private capital joins in. BMDO's cumulative investment of $DOL300M in Small Business Innovation Research (SBIR) since 1985 has seeded some notable successes. BMDO's SBIR, which has helped a fourth of this symposium's speakers, attracts a dollar of private capital for every SBIR dollar. Small US firms raised $DOL200 million from public sale of common stock, doubled in employment, and are attracting a growing pool of private capital to match and expand BMDO's subsidy.

WDM can dramatically increase the capacity in point-to-point transmission and can increase the capacity and routing functionality in local- and wide-area networks. However, there are many systems-level limitations on the bandwidth, number of wavelengths, WDM-device characteristics, and inter-user distance. Systems issues include crosstalk, wavelength chirp, EDFA bandwidth, and nonlinearities. We briefly describe some of these component-related issues and the constraints which they place on WDM systems.

In the next decade, data transmission with speeds at several tens of gigabits per second (Gb/s) and beyond in short-haul local area and metropolitan area computer networks, as well as long- haul telecommunications networks, will be necessary to satisfy the ever increasing demands on bandwidth. Time division multiplexing based transmission systems become increasingly difficult to implement at higher speeds due to the speed limitations of electronics. In addition, these networks based on single wavelength transmission, use the available bandwidth inefficiently. As a result, both timing synchronization and bandwidth sharing among large numbers of users become major challenges. Wavelength division multiplexing (WDM) eases most of these problems; but introduces wavelength synchronization as the primary technical hurdle. The adaptive robust WDM receiver adjusts dynamically to the sources and thus alleviates many of the most serious and costly disadvantages of WDM. The technical burdens of WDM transmission are shifted to the receiver which is designed to accommodate the manufacturing and operating imperfects of the transmitter sources. Consequently, the receiver has then to be more sophisticated, but the added complexity in the receiver is in VLSI, simple PIN diodes, and passive guided wave optics. These components are inherently among the least expensive components in an optoelectronic system. Commercial WDM systems, especially in local area computer network environments, can thus be produced at significantly lower cost.

New coding and modulation techniques formulated specifically for employment with wavelength division multiplexing (WDM) components and systems to significantly increase the number of virtual channels are described and analyzed. It is generally accepted that technical and economic considerations limit a conventional WDM system to less than 32 wavelength channels and, in the near term, most likely to 4 or 8. We assume a 4-wavelength WDM system and impose WDM coding or modulation in which the WDM wavelengths are interpreted as unit vectors in a quasi-orthogonal space. We describe how various combinations of these unit vectors define signatures of the wavelength-space type (WDM-vectors), the wavelength-space-time type (WDM-matrices), or the hybridized WDM-optical CDMA type, each potentially capable of yielding a rich address space, even when the number of WDM wavelengths is small. The topologies, implementation, and performance of these codes is discussed for network and interconnection systems.

A realistic quantum cryptographic system must function in the presence of noise and channel loss inevitable in any practical transmission. We examine the effects of these channel limitations on the security and throughput of a class of quantum cryptographic protocols known as four-state, or BB84. Provable unconditional security against eavesdropping, which is the principal feature of quantum cryptography, can be achieved despite minor channel defects, albeit at a reduced transmission throughput. We present a semi-empirical relation between the fully-secure throughput and the loss and noise levels in the channel. According to this relation, a particular implementation of BB84, based on the frequency-division multiplexing scheme and utilizing commercially available detectors, can reach throughputs as high as 10⁴ - 10⁵ secure bits per second over a practical channel of reasonable quality.

Different optical multiplexing techniques are described for providing parallel, high-speed communication between multiple nodes in a distributed multi-access network. Using compact, 2D arrays of VCSELs and VCSEL-based optical switches, data from different nodes can be multiplexed together in the space, time, or wavelength domain, and then transmitted through a single optical fiber. Each channel can be individually-modulated, time-compressed, and time- multiplexed in a bit-serial fashion into a single, high-speed data stream, while different channels are wavelength-multiplexed on a single optical fiber. Spatial routing is achieved by a distributed optical switching network, in which space and wavelength can be combined to provide wavelength routing without wavelength tuning.

It is well known that either Wavelength Division Multiplexing (WDM) or pulsed Code Division Multiple Accessing (CDMA) can be used as a basic accessing format in structuring an optical communication network or high speed parallel data processor. Each such system has its own inherent advantages and disadvantages when used as the principle format. When the two concepts are combined into a single hybrid WDM/CDMA format, some of the disadvantages of each format can be offset by the presence of the other, producing a more robust networking system with improved communication performance. In this paper these hybrid concepts are presented, and some of their hardware and architecture impacts are developed.

Wavelength Division Multiplexing (WDM) technology can be used to create high-capacity, rearrangeable, survivable networks for the transport of broadband services. A key factor in the successful commercialization of multi-wavelength optical networks is the availability of standards for WDM point-to-point and optical networking transmission systems. International standards recommendations are currently being formulated in the ITU (formerly CCITT) in a number of Study Groups related to multiwavelength transmission systems. In this paper, a review will be presented on the status of the recommendations in the current study period, focusing on point-to-point OC-48 WDM systems. Transmission signal parameters such as reference frequency, frequency spacing, and optical signal power levels, as well as optical supervisory channel specifications are being addressed currently. A future set of specifications related to optical networking systems will be addressed in the study period extending from 1997 to 2000.

We have constructed an optical 2-to-1 packet multiplexor for use in the next generation of digital networks. It has a clear advantage over conventional electronic network nodes because it can support any bit rate, theoretically up to the full bandwidth of a fiber. Since it switches on a packet-by-packet basis, the control electronics are simple and inexpensive. The multiplexor uses electronically-addressed 2 X 2 lithium niobate directional coupler switches to route packets and lengths of fiber to buffer contentious packets. The multiplexor can be cascaded to form a larger 2-to-1 multiplexor with improved packet loss performance. We present theoretical and simulated results (including packet loss rate and optical insertion loss) for this multiplexor. We also contrast the performance of the multiplexor for slotted input versus unslotted input.

The next generation of distributed imaging and visualization environments for diagnostic radiography and C⁴I will require the delivery of a guaranteed quality-of-service by a ultra-high bit rate network. Two aspects of the quality-of-service, the link bit rate and the round-trip packet latency, can be met through the use of transparent third-generation photonic networks. These networks can be implemented using ultra-short optical pulses in conjunction with spectral-domain processing to construct links. These links are combined with transparent photonic packet switches to form the network switching fabric. The quality-of-service is guaranteed by using virtual circuit-switching.

Semiconductor edge emitting lasers are passively aligned to polymeric waveguides on high thermal conductivity substrates. The single mode waveguides are combined to provide a high bandwidth wavelength division multiplexed channel. 3D stacks of the substrates are interconnected electrically and optically for further multiplexing.

The demonstration of real-space electron transfer in (Ga,In)As/(Al,In)As asymmetric double quantum wells is reported. Real-space electron transfer is then shown to be an efficient mechanism to enhance the electroabsorptive properties of optical fiber compatible opto- electronic semiconductor heterostructures.

We report on low-loss, alignment-tolerant coupling between a single quantum well GaAs/AlGaAs laser and a cleaved single mode fiber. The laser has been fabricated using conventional growth and processing techniques. The mode size in the transverse direction is expanded by using a diluted waveguide structure to better match the fiber mode size. The diluted waveguide was realized by reducing the Al mole fraction between the core and the cladding, thus providing weak confinement. Very small far field divergence angles (15 degree(s) (transverse) and 4.5 degree(s) (lateral)) were measured from this device, indicative of the expanded mode. A butt coupling efficiency of 70% was achieved against a theoretically possible 78%. In addition, large misalignment tolerances for a 1 dB excess loss of +/- 2 micrometers in the lateral and +/- 1.5 micrometers in the transverse directions, were measured. The T_o of the device was found to be 112 K, showing that the carrier leakage is not significant despite the diluted nature of the waveguide.

We have developed organic polymeric materials that can be readily made into both multimode and single-mode optical waveguide structures of controlled numerical aperture and geometry, making them excellent candidates for WDM applications. Waveguides are formed lithographically, with the liquid monomer mixture polymerizing upon illumination in the UV via either mask exposure or laser writing. Our waveguides are low loss (0.03 dB/cm at 840 nm multimode) as well as temperature resistant (up to 10 years at 120 degree(s)C), enabling use in a variety of applications. Single-mode structures such as directional couplers have been made via laser writing. We further discuss the fundamental optical properties of these polymers and as they relate to WDM applications. As an example, we discuss an inorganic multimode WDM sensor that has been developed for aerospace applications and its integration with multimode polymer waveguides.

The research activity on WDM transmitter and receiver modules is presented. The integration of laser array and optical combiner as well as demultiplexer and detector array is discussed. The challenges and potential approaches for integrated modules are presented.

Micro-optical tunable Fabry-Perot filters, which utilize micro-electro-mechanical control of the cavity length and therefore the active wavelengths, are attractive components for wavelength division multiplexing applications. These vertical cavity devices are fabricated using selective etching to form an air gap between a free-standing top mirror and a bottom mirror fixed to the semiconductor substrate, and electrostatic force from applied voltage bias is used to control the vertical position of the top mirror and therefore the active wavelength of the filter. Using this approach, we have demonstrated GaAs-based devices with tuning ranges as large as 40 nm near a center wavelength of 960 nm, and maximum tuning voltages are typically 15 - 20 V. Furthermore, a wide variety of integrated components such as tunable light-emitters and lasers have been realized by incorporating a quantum well p-i-n diode into the device active region.

The performance of conventional photodiodes is limited by an intrinsic tradeoff between quantum efficiency and bandwidth. We have successfully demonstrated that resonant-cavity photodiodes can simultaneously achieve high quantum efficiency and wide bandwidths. The resonant-cavity approach increases the absorption through multiple reflections between two parallel mirrors. In addition, the wavelength selective spectral response offers potential advantages for applications where filtering is needed such as wavelength division multiplexing. In this paper, we report on a resonant-cavity, separate absorption and multiplication avalanche photodiode (APD). An avalanche gain of more than 40 has been obtained. The peak external quantum efficiency was measured to be approximately 80% at 890 nm with a spectral response linewidth of less than 7 nm. Without cavity enhancement, the efficiency of these APDs would be less than 5% because the absorbing layer is only 500 angstroms thick. The structure was designed to provide electron injection into the multiplication region because we have determined experimentally that for Al_0.4Ga_0.6As, the electron ionization coefficient is larger than that of the hole. Based on the conventional formulation for excess noise, the ratio of ionization coefficients is as low as (beta) /(alpha) equals 0.2.

We demonstrate a photodetector with a very narrow spectral linewidth (less than 2 angstroms) and a 35 angstroms tuning range is demonstrated. The absorption medium is made up of 3 pairs of InGaAs/GaAs Quantum Wells and the operating wavelength of the photodetector is approximately 960 nm. The photodetector features a horizontal resonant cavity in which feedback is achieved using Distributed Feedback Reflectors (DFB). The DFB gratings have a periodicity of 2850 angstroms and provide feedback through the second order of diffraction. The grating periodicity was chosen to facilitate the coupling of normally incident light into the 0.25 micrometers -thick GaAs waveguide of the cavity through the first order of diffraction. The optical and electrical paths in this photodetector are completely orthogonal. Consequently, this normal incidence horizontal resonant cavity photodetector is completely integrable into Wavelength Division Demultiplexing and other Optoelectronic Integrated Circuits with a potential for high speed operation.

Electro-optic modulators have been used widely in high power, large link budget fiber-optic transmitters for both analog and digital signal transmission applications. The traditional electro-optic modulators are made of lithium niobate single crystals or III-V semiconductors. The recent development of high performance electro-optic polymers has demonstrated a promising future for these materials in the fabrication of a new generation of electro-optic modulators and modulator arrays for externally modulated, wavelength division multiplexed fiber-optic transmission systems. The low dielectric constant, flexibility in device processing, compatibility with semiconductor technology, and potentially very large electro-optic coefficient are very attractive features for wide-band, high efficiency waveguide modulators. To investigate the feasibility of using the new class of materials in electro-optic modulator application, we have fabricated both Mach-Zehnder and straight channel electro-optic modulators using a representative crosslinked electro-optic polymer--polyurethane with Disperse Red 19 side groups. The polymer layers are thermally crosslinked to improve device stability. Electric field poling is used to induce a stable noncentrosymmetric structure in the amorphous polymer films. The optical waveguides are defined by reactive ion etching. The final polymer modulators are packaged in a fiber-ready configuration and can be easily inserted into fiber-optic networks. Modulator parameters related to the device performance are tested for analog transmission system applications. The fabrication techniques and experimental data will be presented along with applications to high capacity wavelength division multiplexed communications systems.

We have developed a conservative and reversible optoelectronic intensity modulator. Two of the inputs are optical and the third in the device's initial implementation is an electrical control signal. The device is essentially a controllable optical routing element. In one state beams incident from opposite sides of the device are reflected and in the other state they are transmitted. Using arrays of these devices, various switching networks can be constructed, including crossbar switches and other regular or irregular architectures. The device itself is composed of quantum wells in a Fabry-Perot cavity. Our device is grown using molecular beam epitaxy (MBE) and can be realized using several materials systems, so that varying wavelengths of operation can be obtained. In addition, the radial thickness non uniformity due to rotation during MBE growth can be exploited to obtain devices operating at different wavelengths on the same wafer. The design of the devices or arrays of devices can be focused on optimizing bandwidth, modulation ratio, voltage, or change in reflectivity, depending on the desired application. In this work we will describe the use of the devices for several systems applications and discuss some further refinements to the device that make it more useful in a systems context.

We will report on an 8-channel laser driver circuit intended to drive arrays of Distributed Feedback (DFB) lasers. These have been incorporated into transmitter modules operating at both 155 Mbit/sec and 2.488 Gbit/sec. Considerable power, cost and packaging savings can be achieved by this approach because the small driver size allows direct coupling of the driver and laser in compact modules, which also reduces the fiber alignment complexity. The peak current delivered to each laser is 60 mA; of this, up to 30 mA can be a DC bias current with the modulation current adjustable up to 30 mA peak-to-peak. The circuit is designed for an input signal of 300 mV differential into 50 Ohms. The modulation currents are separately adjustable for each channel. The circuit uses a differential signal path to achieve good common mode rejection to reduce crosstalk. The drivers were fabricated on a 500 micrometers spacing to match the DFB laser spacing, and care was taken to minimize capacitive coupling and crosstalk between channels. The power dissipation at maximum drive is 2.3 W with all 8 channels active.

The linewidth, chirp and mode-suppression-ratio (MSR) of directly modulated sampled grating DBR (SGDBR) lasers has been measured. Although the tuning range can be up to an order of magnitude larger than in simple DBR lasers (i.e. 60 nm vs 6 nm), we find that the linewidth, chirp and MSR are about the same or better (i.e. (Delta) (nu) < 5 MHz, (alpha) equals 3-8, and MSR > 40 dB) over a wide range of operating parameters. The modulation bandwidth was in excess of 4 GHz, and the dynamic MSR remained > 40 dB as long as the current did not swing below threshold.

A novel approach to optical storage based on layering of cholesteric liquid crystal (CLC) media is being pioneered by Reveo, Inc. CLC media have been chosen due to their unique property of selective reflection, wherein a CLC film reflects light of its characteristic wavelength and polarization handedness at near-zero loss while transmitting all other light. The new technology has the potential of making possible Terabyte storage on a single optical disk. This results from the ability to place 2 MN CLC layers on a single disk and reading selectively one or more such layers. Here M refers to the number of `decks' selected by depth- of-focus means. Each `deck' has 2 N layers selected by means of N wavelengths and two polarization states. It is projected that an enhancement factor of 2 MN of 400 is possible for M equals 10 and N equals 20. Furthermore, reading many layers in parallel promises to increase the data rate. The novel concept has been demonstrated in a 6-layer experiment. This, along with computer simulation indicate that the technology is viable and can go to market earlier than other storage technologies.

In this paper, a new scheme to implement high-density photopolymer-based spatially multiplexed multiwavelength programmable holographic memory is proposed. Two approaches are considered. The first is to implement programmable massive fanout beams based on an electrooptic grating array and the second is aimed at providing a multiwavelength high density memory by obtaining a smaller holographic memory spot at the proposed off- focal plane location. In the first approach, the diffraction efficiency of the electrooptically modulated grating is optimized, and 32.5% +/- 2.5% modulation efficiency is achieved under an applied voltage of 100 volts. In the second approach, the storage density is improved by 100 approximately 110% when compared with that obtained at the focal plane after Fourier transform. All the experimental results agree well with the theoretical predictions. A memory density of 100 pages/mm² is feasible using the reported scheme.

Wavelength division multiplexing (WDM) and demultiplexing (WDDM) devices are considered to be two of the key elements for enhancing the transmission bandwidth of optical communications and sensor systems. During the past 20 years, various type of WDMs and WDDMs have been proposed and demonstrated. Recently the technique for producing spatially multiplexed phase grating based on polymer-based waveguide holograms for WDDM applications has been reported. We report the formation of a surface-normal WDDM using photopolymer-based volume holograms in conjugation with graded index lenses. The elimination of edge-coupling significantly enhances the packaging reliability and the time reversal of the beam propagation automatically results in the required WDM. Furthermore, such a configuration is compatible with the implementation of vertical cavity surface-emitting lasers where the characteristic of azimuthal symmetry is maintained in the waveguiding substrate. In this paper, we present two devices for network applications. The first is an 8 channel surface-normal WDM with a center channel wavelength of 772 nm and a wavelength separation of 4 nm. The second is a 3 X 3 wavelength selective crossbar with a center wavelength of 765 nm and a channel separation of 10 nm. These devices are pivotal for the realization of such a computer-to-computer interconnect network where both WDM and space division multiplexing are employed to enhance the transmission bandwidth. The switching device can be realized using the wavelength-selective crossbar to be presented in this paper.

The coming of age of wavelength-division-multiplexed (WDM) laser arrays is bringing new challenges in the testing of semiconductor lasers. Because of stringent requirements on the laser linewidths and their frequency stability and because of electrical, optical, and thermal crosstalk problems, a new methodology is required for evaluating the performance of WDM laser arrays. This paper describes techniques that will be used to test WDM laser arrays both cw and under pulsed conditions. The laser arrays for these studies will be procured under a new program called `The WDM Alliance' sponsored by BMDO/AFOSR. Preliminary data on monolithic WDM laser arrays are also presented in this paper.

Precise wavelength control in a multi-wavelength laser array is an important issue concerning practical applications. The wavelength is dictated by material and structural parameters. By controlling the waveguide dimension and waveguide orientation the lasing wavelength can be controlled. This can be done by varying the ridge width and ridge angle with respect to the DFB gratings. In this paper, a three-dimensional DFB laser model is presented. This is used to study the extent of wavelength tunability in DFB laser arrays.

WDM semiconductor sources are needed to fulfill the requirements of future high-speed, all- optical fiber networks. The key technical challenge is to meet at the same time all of the tight requirements on wavelength accuracy, stability over time, high-speed operation, simplicity of control electronics, and low cost that practical systems demands. State-of-the-art of WDM component technology is explored and the many available technological options are presented and compared.

This paper describes the digital laser and WDM laser array development at Ortel. First, we optimized the individual laser performance, and then studied the possibility of array integration. The issues of yield, cross-talk and packaging of laser array will be discussed.

Wavelength division multiplexed systems place stringent requirements on the absolute wavelength and wavelength spacing of the elements in laser arrays. Ridge waveguides (RW) show excellent potential for practical implementation due to their simple fabrication with relaxed fabrication tolerances, high reliability and good performance. An analysis of the fabrication tolerances for RW and buried heterostructure (BH) devices is performed, showing the advantages offered by the ridge design. The performance limitations that are common to both BH and RW devices will be discussed. Experimental results for four element distributed feedback ridge laser arrays at 1.55 micrometers will be presented as well.

Multiple-wavelength vertical-cavity surface-emitting laser arrays are fabricated by using a patterned-substrate growth technique and a location-resolvable in situ optical calibration method in a molecular beam epitaxy system. We achieved a record wavelength span of 62.7 nm, highly uniform threshold currents with an average of 2.16 +/- 0.81 mA, and high repeatability of wavelength spacing between 15 arrays with sharp wavelength shift rate of 117.14 nm/mm. Accuracy of 0.28% of high and low wavelength limits and a 2.66 angstroms wavelength standard deviation from 4 X 35 arrays are also obtained.

Wavelength-division-multiplexing (WDM) has long been recognized as an attractive way to exploit the bandwidth of optical fiber. Such systems have been slow to gain commercial acceptance, because of the high cost of WDM components such as Distributed Bragg Reflector lasers and/or Distributed Feedback lasers. We propose that 1300/1550 nm long-wavelength vertical cavity lasers (VCSELs) can be manufactured inexpensively in WDM arrays. VCSELs at 1300/1550 nm have progressed slowly, relative to their 850/980 nm counterparts. In this paper, we review progress in long-wavelength VCSELs, and introduce a new device structure which can provide high CW output power, and wide wavelength operation. We then introduce a method for fabricating VCSELs in WDM arrays, and show initial results.

Wavelength Division Multiplexing (WDM) has become the technology of choice for meeting the rapid increase in demand for bandwidth and capacity in telecommunication and computer networking systems. One of the key enabling technologies for WDM systems is multiwavelength filters. The spectrometer on a chip (SOC) is an integrated optics approach to the implementation of a high performance multiwavelength filter. This paper provides an overview of the design, processing, and testing issues for two types of SOCs: etched grating and phased-array waveguide grating. Both types of devices are used in various WDM components. In addition to wavelength multiplexers/demultiplexers, other integrated WDM photonic devices which utilize SOCs for their wavelength filtering functions will also be discussed.

We examine several critical issues related to laser diodes with wavelength (lambda) approximately 750 - 1000 micrometers for WDM applications. Particular attention was given to the Vertical Cavity Surface Emitting Laser and Distributed Feedback Laser which are the most central components for the optical interconnect or local-area network, or for pumping the Er or Pr doped optical fiber. Regrowth control, stability and reliability at high power and high temperature operation as well as the optimal design are the most critical issues for the devices. Aluminum-free InGaAsP/GaAs is proposed as an alternative to AlGaAS/GaAs for the WDM applications. Perspectives are presented on how those problems especially, reliability and regrowth issues for WDM application can be eased by this material system.

DuPont has developed an optical interconnect technology consisting of polymer materials and fabrication and assembly processes. This technology, referred to as Polyguide, provides the user with the capability to mass produce channel optical waveguides that perform splitting, point to point interconnection, wavelength discrimination and other optical functions. These materials and processes make packaging practical. This has been demonstrated with optical printed wiring boards, connectorized multilayer ceramic modules and discrete pigtailed components. Critical interfacing requirements have also been met. These include the passively aligned attachment of single mode optical fiber arrays and the fabrication of low loss mirrors for coupling to laser diodes, LEDs, and photodectors. As part of the ARPA funded POLO project DuPont is advancing the fabrication and assembly processes to allow low cost deployment of optical interconnects. A description of current Polyguide technology and performance specifications will be presented. Demonstrations of packaging will be reviewed. This polymer system addresses most of the tasks required for the practical utilization of optical waveguides. Polyguide technology can enable optical connectivity and transmission in many new products.

Wavelength division multiplexers (WDMs) with high-wavelength-shift-tolerance (HWST) are proposed for both multi-mode and single-mode regimes, based on a 1:1 magnification transmission lens imaging system combined with a Littrow grating configuration. The HWST WDMs have a high wavelength-packing-ratio; up to 1:2. In this paper, their optical properties are discussed, and related technological problems are analyzed. In addition, design and experimental results, as well as current applications for both multi- and single-mode WDM devices are provided.

The spectral response of a chirped sinusoidal surface relief grating in an optical waveguide has been studied by means of Local Normal Mode Expansion theory. A matrix technique has been applied to account for the varying grating period. The grating is divided into segments with constant periods and coupling coefficients. Nonslanted grating is considered in a first-order diffraction. Also, contradirectional coupling between guided modes in phase synchronism at an arbitrary angle of incidence is considered. Performance considerations include TE-TE, TE- TM, and TM-TM mode coupling for different grating geometry and waveguide parameters. We show the effect of geometry and waveguide parameters on the performance of the chirped grating as a wavelength demultiplexer. Also, we demonstrate how the filtering and demultiplexing characteristics and the spectral shift between different polarization modes can be controlled.

This paper addresses the issue of inserting WDM (wavelength division multiplexing) and amplifier technologies into optical networks from network system architecture and application perspectives. In order to facilitate technology transfer into commercial applications, we need to carefully consider where we can insert the technologies, how we should utilize the technologies, and what are the benefits of employing these technologies. Through years' of investigation and development, taking into considerations of optical network environment, benefits of the technologies and implementation feasibility, we believe that there are three major roles that WDM and amplifier technologies can play in optical networks: point-to-point transmission for capacity expansion, in-fiber out-of-band control for format transparency, and optical routing for network efficiency. In this paper, we will describe each of these roles and their benefits. Progress and results of our related research programs, including optical crossbar switch testbed, will be reported.