Abstract: The Lorentzian-shape filter response of a microring resonator filter is not suitable for practical use in wavelength division multiplexing (WDM) systems because of the lack of passband flatness, high crosstalk, and the large wing in the rejection band. Therefore, the tailoring of filter response shape is required to improve the performance. The series coupled microring resonator is one of the solutions. We designed and fabricated vertically triple coupled microring resonator add/drop filters with a stacked configuration. A box-like filter response with a flat passband was successfully obtained, and the free spectral range (FSR) was expanded to 25.8 nm owing to the Vernier effect.

Abstract: A novel shape-adjustable narrowband optical filter utilizing stimulated Brillouin scattering in an optical fiber is proposed and demonstrated. In this scheme, binary-phase-shift-keying modulation is applied to the pump wave to broaden and shape the Brillouin gain spectrum. By choosing an appropriate modulation data pattern, we realized a flat-top steep-cutoff optical bandpass filter with a 3-dB bandwidth of 1.5 GHz and a 10-dB bandwidth of 2 GHz is realized. In addition, a tunable optical notch filter is also realized by deamplification of the anti-Stokes wave.

Abstract: We theoretically investigated the performance of the photonic crystal superprism, that is, the propagating beam quality, the wavelength sensitivity, and the resolution as a narrow band filter at 1.5-μm-wavelength range. First, we defined the equi-incident-angle curve in the Brillouin zone. Next, we mapped three parameters that represented the abovementioned performance over the Brillouin zone. As a result, we found a narrow design window that allows a high resolution of 0.4 nm along an equi-incident-angle curve but requires an incident beam width of over 100 μm and a device length of centimeter order. It can be an essential high efficiency filter if the input end of the crystal is optimized and the propagation loss is suppressed.

Abstract: A key device in all-optical networks is the optical filter. A ring resonator filter with an integrated semiconductor optical amplifier (SOA) on the basis of GaInAsP-InP has been investigated and fabricated. A required passband shape of loss-compensated ring resonator filters can be custom-designed by the use of multiple coupled resonators. Results of single-, double-, and triple-ring resonators with integrated SOAs with free spectral ranges of 12.5, 25, and 50 GHz, respectively, are presented. A box-like filter response is obtained by the double- and triple-ring resonators using specific coupling coefficients.

Abstract: The present invention suppresses to a minimum the degradation of the transmission quality caused by chromatic dispersion characteristic of an optical transmission medium, and the interplay between the chromatic dispersion and non-linear optical effects in dense WDM transport systems A baseband input data signal is precoded in advance by a pre-coding unit (2), phase modulation is carried out using a precoded signal by the optical phase modulating unit (3), and the phase modulated optical signal is converted to an RZ intensity modulated signal by the optical filter unit (5) that performs phase-shift-keying to amplitude-shift-keying conversion For example, an optical phase modulating unit (3) generates an encoded DPSK phase modulated signal using a differential phase shirt keying (DPSK) format, and a phase modulated signal is converted to an RZ intensity modulated signal by the optical filter unit (5) disposed downstream of the optical phase modulating unit (3)

Abstract: We describe a novel approach to implementing wide-field-of-view narrow-band spectral filters, using an array of resonant nanocavities consisting of periodic defects in a two-dimensional three-material photonic-crystal nanostructure. We analyze the transmissivity of this type of filter for a range of wavelengths and in-plane incidence angles as a function of the defect's refractive index, the number of layers in the photonic-crystal reflectors, and the period of the defects and find that this structure diminishes the angular sensitivity of the resonance condition relative to that of a standard multilayer filter.

Abstract: Summary form only given. We have proposed a novel optical orthogonal frequency division multiplexing technique that can overcome the spectral efficiency limitation of the conventional WDM system. This scheme permits substantial overlapping of the spectrum and can achieve the spectral efficiency up to 1 bit/s/Hz in principle. For demultiplexing, we used a newly developed optical discrete Fourier transformer (DFT) instead of electrical digital processing, which is impossible to apply in the optical frequency range. The optical DFT was realized by using a set of delay lines, a phase shifter and a coupler in the frequency domain and bit synchronization and an optical gate in the time domain. In experimental demonstration of this scheme, error-free operation was obtained with a 0.8 bit/s/Hz of spectral efficiency.

Abstract: Semiconductor microdisk resonator lasers vertically coupled to bus waveguides are demonstrated for the first time. These structures have many of the characteristics required for a light source in photonic integrated circuits because they can be coupled to other optical elements (switches, routers, filters, etc.) through common bus lines. A continuous-wave single-mode laser at 1579 nm with a side-mode suppression ratio greater than 30 dB has been achieved for an 8- m-radius microdisk. For larger disks, mode competition between modes near the maximum gain wavelength is observed from the light output-current ( - ) characteristics. Improved heat sink design is required for future devices.

Abstract: We propose and demonstrate a novel technique for 40- and 10-Gb/s chromatic dispersion monitoring that uses an optical filter to select the upper and lower vestigial-sideband (VSB) signals in the transmitted optical data and determine the relative clock phase shift caused by dispersion. Without modification of transmitters, this technique provides low cost chromatic dispersion monitoring for WDM systems, <3 ps/nm dispersion resolution for 40-Gb/s data, and greatly reduced sensitivity to the influence of polarization mode dispersion.

Abstract: Preface. Acknowledgments. List of Physical Constants. Introduction. 1. The Physics of Optical Components. 1.1. Introduction. 1.2. The Nature of Light. 1.2.1. The Wave Nature of Light. 1.2.2. The Particle Nature of Light. 1.2.3. Huygens-Fresnel Principle. 1.2.4. Interference. 1.2.5. Holography. 1.2.6. Optical Correlators and Storage. 1.2.7. Light Attributes. 1.3. Optical Materials. 1.3.1. Transparent Versus Opaque Matter. 1.3.2. Homogeneity and Heterogeneity. 1.3.3. Isotropy and Anisotropy. 1.3.4. Organic Materials. 1.3.5. Photochromaticity. 1.4. Light Meets Matter. 1.4.1. Reflection and Refraction: Snell's Law. 1.4.2. Critical Angle. 1.4.3. Antireflection. 1.4.4. Prisms and Superprisms. 1.4.5. Propagation of Light. 1.4.6. Diffraction. 1.4.7. Polarization. 1.4.8. Extinction Ratio. 1.4.9. Phase Shift. 1.4.10. Birefringence. 1.4.11. Material Dispersion. 1.4.12. Electro-Optic Effects. 1.4.13. Material Attributes. 1.5. The Fiber as an Optical Transmission Medium. 1.5.1. Composite Refractive Indices. 1.5.2. Fiber Modes. 1.5.3. Fiber Attenuation and Power Loss. 1.5.4. Fiber Birefringence. 1.5.5. Dispersion. 1.5.6. Spectral Broadening. 1.5.7. Self-Phase Modulation. 1.5.8. Self-Modulation or Modulation Instability. 1.5.9. Effect of Pulse Broadening on Bit Error Rate. 1.6. Nonlinear Phenomena. 1.6.1. Stimulated Raman Scattering. 1.6.2. Stimulated Brillouin Scattering. 1.6.3. Four-Wave Mixing. 1.6.4. Temporal FWM, Near-End and Far-End. 1.6.5. Impact of FWM on DWDM Transmission Systems. 1.6.6. Countermeasures to Reduce FWM. 1.7. Solitons. 1.8. Summary of Nonlinear Phenomena. 1.9. Factors that Affect Matter and Light. 1.10. Regarding Optical Fiber. 1.10.1. Ideal Fiber Versus Real Fiber. 1.10.2. The Evolving Bandwidth-Span Product. 1.10.3. Fiber Amplifiers and Spectral Continuum. 1.10.4. New Fibers. 1.10.5. How Strong Is Fiber? 1.11. Fiber Connectivity. 1.12. Optical PWBs. Exercises. References. Standards. 2. Optical Components. 2.1. Introduction. 2.1.1. Geometrical Optics. 2.1.2. Insertion Loss and Isolation. 2.1.3. Parameters Common to All Components. 2.2. Optical Filters. 2.2.1. Fabry-Perot Interferometer. 2.2.2. Dielectric Thin Film. 2.2.3. Diffraction Gratings. 2.2.4. Bragg Gratings. 2.2.5. Mach-Zehnder Interferometry. 2.2.6. Arrayed Waveguide Grating Filters. 2.2.7. Polarizing Filters. 2.2.8. Absorption Filters. 2.2.9. Acousto-Optic Tunable Filters. 2.2.10. Hybrid Filters. 2.2.11. Comparing Tunable Filters. 2.3. Optical Directional Couplers. 2.4. Optical Power Attenuators. 2.5. Polarizers and Rotators. 2.6. Beam Splitters. 2.7. Optical Isolators and Circulators. 2.8. Quarter-Wavelength and Half-Wavelength Plates. 2.9. Optical Multiplexers and Demultiplexers. 2.9.1. Prisms and Superprisms. 2.9.2. Gratings. 2.9.3. Mach-Zehnder Demultiplexer. 2.9.4. Arrayed Waveguide Grating Demultiplexers. 2.9.5. Channel Interleavers and Channel Splitters. 2.10. Optical Cross-Connects. 2.10.1. Free-Space Optical Switching. 2.10.2. Solid-State Cross-Connects. 2.10.3. Polymers and Inks. 2.10.4. Photochromic Materials. 2.10.5. Technologies and Switching Speeds. 2.11. Optical Add-Drop Multiplexers. 2.12. Optical Equalizers. 2.13. Light Sources. 2.13.1. Light-Emitting Diodes. 2.13.2. Lasers. 2.14. Laser Beams. 2.14.1. Gaussian Beams. 2.14.2. Near-Field and Far-Field Distribution. 2.14.3. Peak Wavelength. 2.14.4. Degree of Coherence. 2.14.5. Laser Safety. 2.15. Modulators. 2.15.1. Types of Modulators. 2.15.2. A Case: Amplitude Modulation. 2.15.3. Modulation and Bit Error Probabilities. 2.16. Photodetectors and Receivers. 2.16.1. The PIN Photodiode. 2.16.2. The APD Photodiode. 2.16.3. Photodetector Figure of Merit. 2.16.4. ITU-T Nominal Center Frequencies. 2.17. Optical Amplifiers. 2.17.1. Semiconductor Optical Amplifiers. 2.17.2. Rare Earth-Doped Fiber Optical Amplifiers. 2.17.3. Optical Parametric Amplifiers. 2.17.4. Raman Amplifiers. 2.17.5. Synergistic Amplification. 2.17.6. Stimulated Brillouin Scattering. 2.17.7. Amplification in the Low-Loss Spectral Range. 2.18. Wavelength Converters. 2.18.1. Cross-Gain Modulation. 2.18.2. Cross-Phase Modulation. 2.18.3. Four-Wave Mixing. 2.18.4. Optical Frequency Shifting. 2.19. Optical Phase-Locked Loops. 2.20. Ring Resonators. 2.21. Optical Attenuators. 2.22. Optical Signal-to-Noise Ratio. 2.22.1. Bit Error Rate. 2.22.2. BER and Eye Diagram. 2.23. New Materials and Components. 2.23.1. Optical Materials. 2.23.2. Hollow Fibers. 2.23.3. Lasers and Receivers. 2.23.4. Optical Cross-Connects. 2.23.5. Optical Memories. 2.23.6. Optical Integration. Exercises. References. Standards / 233 3. Communications Fundamentals. 3.1. Introduction. 3.2. Pulse Coded Modulation. 3.3. Loop Accessing Methods. 3.3.1. xDSL. 3.3.2. Other High-Speed Short-Reach Technologies. 3.4. Time Division Multiplexing Systems. 3.4.1. Access and Pair-Gain Systems. 3.4.2. Fiber-to-the-Home Technology. 3.4.3. Switching Systems. 3.4.4. Digital Cross-Connect Systems. 3.5. Getting Connected. 3.6. Data Systems. 3.6.1. The OSI Model. 3.6.2. Local Area Networks. 3.6.3. Packet Networks. 3.6.4. Frame Relay. 3.6.5. ATM. 3.6.6. Quality of Service. 3.7. SONET and SDH. 3.7.1. SONET Topologies. 3.7.2. SONET and SDH Rates. 3.7.3. SONET and SDH Frames. 3.7.4. Floating Frames and Pointers. 3.7.5. Overhead Definition. 3.7.6. Frequency Justification. 3.7.7. Path Overhead. 3.7.8. Maintenance. 3.7.9. Operations Communications Interface. 3.7.10. Interworking. 3.7.11. Next-Generation SONET. 3.8. Internet. 3.8.1. Voice over IP. 3.8.2. Fax over IP (FoIP). 3.8.3. ATM over SONET. 3.8.4. IP over SONET. 3.9. Optical Networks. 3.10. What Is a DWDM System and Network? Exercises. References. Standards. 4 .DWDM Systems. 4.1. Introduction. 4.2. DWDM Network Topologies-Review. 4.3. DWDM Systems and Network Layers. 4.3.1. DWDM and Standards. 4.3.2. Domains or Functions. 4.3.3. System Partitioning and Remoting. 4.4. Key Building Blocks of a DWDM System. 4.4.1. Transmitters and Receivers. 4.4.2. Optical Amplifiers and Regenerators. 4.4.3. Dispersion Compensating Solutions. 4.4.4. Optical Gain Equalizers. 4.4.5. Optical Wavelength Translators. 4.4.6. Timing. 4.4.7. Optical Switching. 4.4.8. Control Architectures and Controllers. 4.4.9. Interfaces. 4.5. Wavelength Management Strategy. 4.6. Equipment Sensing Strategy. 4.7. Fault Detection and Reporting Strategy. 4.7.1. Fault Detection on the Network Level. 4.7.2. Fault Detection Identifiers. 4.7.3. Overhead, Data, and Error Correction: The Digital Wrapper. 4.8. Power Strategy. 4.9. DWDM Systems by Network Layer. 4.9.1. Point-to-Point Systems. 4.9.2. Large Optical Cross-Connect Systems. 4.9.3. DWDM Metro Systems. 4.9.4. Access DWDM Systems and First/Last Mile. 4.10. Protected and Unprotected Systems. 4.11. Engineering DWDM Systems. 4.11.1. Parameters That Influence Optical Design. 4.11.2. ITU-T Recommended Frequencies. 4.11.3. Channel Capacity, Width, and Spacing. 4.11.4. Channel Bit Rate and Modulation. 4.11.5. Multichannel Frequency Stabilization. 4.11.6. BER and Channel Performance. 4.11.7. Channel Dispersion. 4.11.8. Power Launched. 4.11.9. Optical Amplification and Compensation. 4.11.10. The Fiber-Medium and Limitations. 4.11.11. Optical Power Budget. 4.11.12. Power Budget Calculations by Example. Conclusions. Exercises. References. Standards. 5. DWDM Networks. 5.1. Introduction. 5.1.1. Multiprotocol Label Switching. 5.1.2. MPlambdaS. 5.1.3. DiffServ, IntServ, and MPLS. 5.1.4. Optical Virtual Path Network. 5.1.5. Network Layers and Protection. 5.1.6. The Evolving Telecommunications Management Network. 5.2. The Optical Transport Network. 5.3. DWDM Network Topologies and Restoration Strategies. 5.3.1. Point-to-Point Topology. 5.3.2. Ring Topology. 5.3.3. Mesh Topology. 5.3.4. Ring-Mesh Networks. 5.4. Dispersion Management. 5.5. Bandwidth Management. 5.5.1. Wavelength Management. 5.5.2. Traffic Management. 5.5.3. Congestion Management. 5.6. Fiber Span Between Transmitter and Receiver. 5.7. Fault Management. 5.8. Network Security. 5.9. DWDM Network Issues. 5.9.1. Interoperability and Internetworking. 5.9.2. Optical Performance Monitoring. 5.9.3. Network Future-Proofing. 5.9.4. Wavelength Sharing. 5.9.5. IP/SONET over DWDM. 5.9.6. Maintenance. 5.9.7. DWDM Network Management. 5.10. Wireless DWDM Networks. Exercises. References. Standards. 6. Emerging Technologies. 6.1. Introduction. 6.2. Emerging Technologies. 6.2.1. Theory and New Materials. 6.2.2. Communications Components, Systems, and Networks. 6.2.3. Intelligent Homes. 6.2.4. Intelligent Transportation. 6.2.5. Intelligent Powering Systems. 6.3. Current Research. 6.3.1. Advanced Lasers. 6.3.2. Artificial Optical Materials. 6.3.3. Optical Cross-Connect. 6.3.4. Optical Memories and Variable Delay Lines. 6.3.5. Nonintrusive Optical Sensors. 6.4. Conclusion. References. Standards. Answers to Exercises. Acronyms. Index. About the Author.

Abstract: The filter response of single-ring resonators with integrated semiconductor optical amplifiers based on GaInAsP-InP is presented. The devices with free spectral ranges of 25 and 50 GHz have the form of a racetrack. An on-off ratio of 20 dB, a full-width at half-maximum of 12 and 24 pm, a finesse of 17, and a Q factor of 130,000 and 65,000, respectively, have been achieved. The tuning to a specific wavelength is performed by using integrated Pt-resistors.

Abstract: A wavelength tunable optical filter 14 and a method of making the same The optical filter 14 comprising two back-to-back Fabry-Perot optical cavities 30 & 40 comprising a fixed mirror 31 common to both cavities with parallel displaceable mirrors 32 & 42 located one on each side of the fixed mirror 31 to adjust the overall known length of the respective cavities One optical cavity may have greater length than the other optical cavity

Abstract: This paper describes a theoretical and experimental analysis of the channel drop filter using a single defect formed near the two-dimensional (2-D) photonic crystal slab waveguide. First, we calculate the transmission spectrum of a 2-D photonic crystal waveguide and show that high transmittance for a wide wavelength range (/spl sim/60 nm) is obtained in the 1.55-/spl mu/m region. We also show that a defect state having a wavelength within the high transmission wavelength range can be formed in the photonic bandgap by introducing a single defect of appropriate radius. Next, we fabricate several devices and show that the emission wavelength from each defect can be tuned by changing the defect radius. The measured tuning characteristics coincide well with the calculated results. From the near-field pattern of the device, we estimate the emission efficiency of the present device at almost a few tens percent. We clarify the structural condition in order to obtain the maximum output efficiency and show that tuning of emission wavelength while maintaining high output efficiency is possible by selecting appropriate defect radius and position. Based on these results, we propose an ultrasmall channel drop filter for a wavelength-division-multiplex optical communication system.

Abstract: An dynamic optical filter 10 is provided to selectively attenuate or filter a wavelength band(s) of light (i.e., optical channel(s)) or a group(s) of wavelength bands of an optical WDM input signal 12. The optical filter is controllable or programmable to selectively provide a desired filter function. The optical filter 10 includes a spatial light modulator 36, which comprises an array of micromirrors 52 effectively forms a two-dimensional diffraction grating mounted in a retro-reflecting configuration. Each optical channel 14 is dispersed separately or overlappingly onto the array of micro-mirrors 52 along a spectral axis or direction 55 such that each optical channel or group of optical channels are spread over a plurality of micro-mirrors to effectively pixelate each of the optical channels or input signal. Each channel 14 or group of channels may be selectively attenuated by flipping or tilting a selected number of micro-mirrors to thereby deflect a portion of the incident radiation away from the return optical path. The micro-mirrors operate in a digital manner by flipping between a first and second position in response to a control signal 56 provided by a controller 58 in accordance with an attenuation algorithm and an input command 60. The switching algorithm may provide a bit (or pixel) map or look-up table indicative of the state of each of the micro-mirrors 52 of the array to selectively attenuate the input signal and provide a modified output signal 38 at optical fiber 40.

Abstract: We present a microspectrometer based on a tunable interference filter for infrared or visible light that scans the desired part of the spectrum within milliseconds. A single pixel detector measures serially the intensity at selected wavelengths. This concept avoids expensive linear detectors as used for grating spectrometers. The tunable filter is fabricated by a new porous silicon technology using only two photolithography steps. A Bragg mirror or a Fabry-Perot bandpass filter for transmission wavelengths between 400 nm and 8 /spl mu/m at normal incidence is created by modulations of the refractive index in the filter plate. Two thermal bimorph micro-actuators tilt the plate by up to 90/spl deg/, changing the incidence angle of the beam to be analyzed. This tunes the wavelength transmitted to the detector by a factor of 1.16. The filter area can be chosen between 0.27 /spl times/ 0.70 mm/sup 2/ and 2.50 /spl times/ 3.00 mm/sup 2/, the filter thickness is typically 30 /spl mu/m. The spectral resolution of /spl Delta//spl lambda///spl lambda/ = 1/25 is sufficient for most sensor applications, e.g., measurement of CO/sub 2/ and CO in combustion processes by their IR absorption bands as will be presented.

Abstract: Under the assumption that small-scale irradiance fluctuations are modulated by large-scale irradiance fluctuations, we developed a heuristic model of irradiance fluctuations for a propagating optical wave in a weakly inhomogeneous medium This model takes into account the loss of spatial coherence as the optical wave propagates through atmospheric turbulence by eliminating effects of certain turbulent scale sizes that exist between two scale size, hereafter called the upper bound and the lower bound These mid-range scale size effects are eliminated through the formal introduction of spatial frequency filters that continually adjust spatial cutoff frequencies as the optical wave propagates By applying a modification of the Rytov method that incorporates an amplitude spatial frequency filter function under strong fluctuation conditions, tractable expressions are developed for the scintillation index of a Gaussian beam wave that are valid under moderate- to-strong irradiance fluctuations Inner scale effects are taken into account by use of a modified atmospheric spectrum that exhibits a bump at large spatial frequencies We also include the effect of a finite outer scale in addition to inner scale

Abstract: PROBLEM TO BE SOLVED: To make possible production of large quantity and low price in spite of miniaturization in an image pickup lens unit available for an image pickup device. SOLUTION: Lenses 1, 2 and 4 provided with powers as optical elements are overlapped in the direction of the optical axis and an optical filter 3 is inserted between the lenses 2 and 4. The adjacent optical elements are bonded while being positioned to match optical axes in the direction orthogonal to the optical axes to provide an appropriate interval in the direction of the optical axis by a positioning part provided on the lateral side of each of the optical elements. The optical element arrays are overlapped and cut by a cutting line to produce the image pickup lens unit. COPYRIGHT: (C)2004,JPO

Abstract: An optical modulating device capable of use as a light valve, display, or optical filter, which uses variation in incident angle to exploit color-selective absorption at a metal-dielectric interface by surface plasmons. The device includes a dielectric layer, at least one metallic layer through which electromagnetic radiation may be transmitted or reflected, and incident and exit layers which are both optically transmissive. A beam steering mechanism controls the incident angle of the electromagnetic radiation. In one embodiment, an external beam steering mechanism is used to set the incident light angle onto the filter. In another embodiment, the filter is formed as an integral part of, for example, a cantilever. The incident light angle is then controlled by the angle of the filter cantilever.

Abstract: The idea of implementing optical filters by coupling evanescent waves from several diffracted orders into multiple leaky waveguide modes is studied theoretically. Using a dielectric thin-film structure consisting of a coupling grating placed between adjacent waveguides, guided-mode resonance filters exhibiting multiple reflection peaks within a specified wavelength range can be obtained. These peaks originate in the resonant waveguide modes that are excited by the diffracted waves dispersed by the grating. It is shown that this device can be used to realize multiwavelength as well as wide-band spectral filters.

Abstract: We have proposed and demonstrated a novel approach to multi-channel tunable dispersion compensation using all-pass multi-cavity etalon filters for 10 Gb/s applications.

Abstract: We propose and demonstrate a simple method to improve both the receiver sensitivity and spectral efficiency of the optical duobinary transmission system. Compared to the conventional duobinary signal generated by using an electrical low-pass filter, more than 1-dB improvement of receiver sensitivity and /spl sim/20% reduction in the spectral width are achieved simply by filtering the 10-Gb/s duobinary signals with a narrow-bandwidth (7 GHz) optical filter.

Abstract: We have investigated the utility of wavelet filters for enhanc- ing contrast in the digital speckle pattern interferometric fringes obtained from a vibrating loudspeaker diaphragm and from the vibrating bracket of an electric motor. Experimental results reveal that use of properly chosen other filters along with the wavelet filter gives better enhancement. Our investigations also show that if the data are preprocessed by median filtering before implementing the wavelet filtering, then a weakly diffusing object requires a higher-kernel filter and strongly diffusing object requires lower-kernel one. © 2002 Society of Photo-Optical Instrumentation Engineers.

Abstract: The present invention provides a MEMS-based tunable Fabry-Perot filter (100) that is more reliable, more cost effective and exhibits better performance than prior art tunable optical filters.

Abstract: We provide a detailed analysis of the various problems connected with the development of tunable thin-film filters for wavelength-division multiplexing applications. We examine the relation between the change in layer thickness and the central wavelength shift for various configurations and point out the significance of the structure of the reflectors, the spacer thickness, and the location of the active layers. We describe and compare practical arrangements using either temperature or an electric field as the driving parameter.

Abstract: A new photonic signal processor topology that simultaneously achieves both a high-Q and a high skirt selectivity and stopband attenuation filter response is presented. It is based on a novel dual-cavity bandpass optical structure in which two pairs of active fiber Bragg grating cavities are used with an optical gain offset to control the poles and stopband attenuation characteristics of the filter. This concept enables a large improvement in the filter stopband attenuation, rejection bandwidth, and skirt selectivity to be realized. Measured results demonstrate both a narrow bandpass bandwidth of 0.4% of center frequency and a skirt selectivity factor of 16.6 for 40 dB rejection, which corresponds to a 6.5-fold improvement in comparison to conventional single cavity high-Q structures. To our knowledge, this is the best skirt selectivity reported for a photonic bandpass filter to date. The new photonic filter structure has been experimentally verified and excellent agreement between measured and predicted responses is shown.

Abstract: With the normal modulation method, it is difficult to construct a Hilbert transform device because it is complicated. To solve the problem, the present invention generates a single sideband modulated optical pulse train by driving a Mach-Zehnder optical modulator for optical pulse generation with a laser source's sine wave clock signals rendered 90 degrees out of phase from each other. The generated pulse train is entered into an optical modulator, modulated with an NRZ (nonreturn-to-zero) data signal, and filtered by a narrow-band optical filter to obtain one of two sidebands.

Abstract: Adaptive optical amplifiers with dynamic optical filters and feedback control. Dynamic optical filters may include micromirror devices with wavelength spreading for re-configurable wavelength attenuation.

Abstract: We demonstrate a novel device that comprises a pair of broadband and narrowband long-period gratings written in specially designed few-mode fibers to achieve in-fiber bandpass filtering. This device configuration opens the possibility of using long-period gratings for complex spectral shaping in a band-selection as opposed to the conventional band-rejection configuration. The devices are low loss <0.5 dB as well as tunable over large spectral ranges (26 nm). We demonstrate, for the first time to our knowledge, that the unique dispersive properties of long-period gratings allow for constructing dispersion-free bandpass filters with arbitrarily sharp spectral profiles.