Three-Dimensional Optical Data Storage Using Photochromic Materials.

Wavelength multiplexers, demultiplexers and routers based on optical phased arrays play a key role in multiwavelength telecommunication links and networks. In this paper, a detailed description of phased-array operation and design is presented and an overview is given of the most important applications.

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PHASAR-based WDM-devices: Principles, design and applications

WDM networks make a very effective utilization of the fiber bandwidth and offer flexible interconnections based on wavelength routing. In high capacity, dynamic WDM networks, blocking due to wavelength contention can he reduced by wavelength conversion. Wavelength conversion addresses a number of key issues in WDM networks including transparency, interoperability, and network capacity. Strictly transparent networks offer seamless interconnections with full reconfigurability and interoperability. Wavelength conversion may be the first obstacle in realizing a transparent WDM network. Among numerous wavelength conversion techniques reported to date, only a few techniques offer strict transparency. Optoelectronic conversion (O/E-E/O) techniques achieve limited transparency, yet their mature technologies allow deployment in the near future. The majority of all-optical wavelength conversion techniques also offer limited transparency but they have a potential advantage over the optoelectronic counterpart in realizing lower packaging costs and crosstalk when multiple wavelength array configurations are considered. Wavelength conversion by difference-frequency generation offers a full range of transparency while adding no excess noise to the signal. Recent experiments showed promising results including a spectral inversion and a 90 nm conversion bandwidth. This paper reviews various wavelength conversion techniques, discusses the advantages and shortcomings of each technique, and addresses their implications for transparent networks.

Wavelength conversion technologies for WDM network applications

Fiber-optic communication systems form the high-capacity transport infrastructure that enables global broadband data services and advanced Internet applications. The desire for higher per-fiber transport capacities and, at the same time, the drive for lower costs per end-to-end transmitted information bit has led to optically routed networks with high spectral efficiencies. Among other enabling technologies, advanced optical modulation formats have become key to the design of modern wavelength division multiplexed (WDM) fiber systems. In this paper, we review optical modulation formats in the broader context of optically routed WDM networks. We discuss the generation and detection of multigigabit/s intensity- and phase-modulated formats, and highlight their resilience to key impairments found in optical networking, such as optical amplifier noise, multipath interference, chromatic dispersion, polarization-mode dispersion, WDM crosstalk, concatenated optical filtering, and fiber nonlinearity

Advanced Optical Modulation Formats

From the Publisher:
A Unique, Cutting-Edge Approach to Optical Filter Design With more and more information being transmitted over fiber-optic lines, optical filtering has become crucial to the advanced functionality of todays communications networks. Helping researchers and engineers keep pace with this rapidly evolving technology, this book presents digital processing techniques for optical filter design. This higher-level approach focuses on filter characteristics and enables readers to quickly calculate the filter response as well as tackle larger and more complex filters. The authors incorporate numerous theoretical and experimental results from the literature and discuss applications to a variety of systemsincluding the new wavelength division multiplexing (WDM) technology, which is fast becoming the preferred method for system upgrade and expansion. Special features of this book include:
*The theory underlying various architectures that can approximate any filter function
*Filter design techniques applicable to a broad range of materials systemsfrom silica to fiber to microelectromechanical (MEM) systems
*Design examples relevant to filters for WDM systems and planar waveguide devices
*250 figures as well as problem sets for use in graduate-level studies

Optical Filter Design and Analysis: A Signal Processing Approach

The integrated operation of a 16*1 wavelength-division-multiplexed (WDM) source with distributed Bragg reflector (DBR) lasers and electroabsorption modulators has been demonstrated. By using repeated holographic exposures and wet chemical etching, 16 different wavelengths from 1.544 to 1.553 mu m with an average channel spacing of 6 AA are obtained. A high-performance combiner is used to obtain a very uniform coupling into the single-output waveguide, and with the integration of an optical amplifier an average optical power of -8 dBm per channel is coupled into a single-mode fiber. >

A 16*1 wavelength division multiplexer with integrated distributed Bragg reflector lasers and electroabsorption modulators

A multiquantum-well optical amplifier for 1.5- mu m wavelength operation using alternating tensile and compressively strained wells in the active region is described. For each bias level measured, the polarization sensitivity of the amplifier gain is 1 dB or less averaged over the gain bandwidth. This amplifier is suitable for integration with other optical devices in photonic integrated circuits which require polarization-independent gain. >

1.5 mu m multiquantum-well semiconductor optical amplifier with tensile and compressively strained wells for polarization-independent gain

A six-wavelength laser array with an integrated amplifier and modulator designed for transmission of a single selectable wavelength is demonstrated. The lasers have thresholds of ~20 mA, and the single-step printed gratings yield an average channel spacing of 200 GHz. Output powers through the modulator of several milliwatts are obtained from all six lasers when 75 mA is applied to the amplifier.

Six wavelength laser array with integrated amplifier and modulator

A novel monolithic semiconductor laser is demonstrated. The optical cavity comprises a 1/spl times/N waveguide grating multiplexer connected to N optical amplifiers. By driving a specific output port, laser oscillation is obtained at the wavelength determined by the wavelength path through the multiplexer. Such a laser is very useful for WDM systems because it is capable of producing a comb of precisely spaced frequencies. >

Digitally tunable laser based on the integration of a waveguide grating multiplexer and an optical amplifier

A 5.5-mm-long monolithic extended-cavity laser with an integrated Bragg-reflector in the InGaAsP system for active mode-locking at low repetition rates at a wavelength of 1.55 mu m has been fabricated. The device, which is designed to be used as a pulse source in long-distance soliton systems and optical time-division multiplexed systems, generates 20-ps-wide transform-limited pulses with a time-bandwidth product of 0.34 at a repetition rate of 8.1 GHz. >

M. D. Chien

Papers

A 16*1 wavelength division multiplexer with integrated distributed Bragg reflector lasers and electroabsorption modulators

1.5 mu m multiquantum-well semiconductor optical amplifier with tensile and compressively strained wells for polarization-independent gain

Six wavelength laser array with integrated amplifier and modulator

Digitally tunable laser based on the integration of a waveguide grating multiplexer and an optical amplifier

5.5-mm long InGaAsP monolithic extended-cavity laser with an integrated Bragg-reflector for active mode-locking