Showing papers on "Optical filter published in 2006"
TL;DR: In this paper, several photonic signal processors, including high-resolution microwave filters, widely tunable filters, arbitrary waveform generators, and fast signal correlators, are discussed, and a new concept for realizing multiple-tap coherence-free processor filters, based on a new frequencyshifting technique, is presented.
Abstract: Photonic signal processing offers the prospect of realizing extremely high multigigahertz sampling frequencies, overcoming inherent electronic limitations. This stems from the intrinsic excellent delay properties of optical delay lines. These processors provide new capabilities for realizing high time-bandwidth operation and high-resolution performance. In-fiber signal processors are inherently compatible with fiber-optic microwave systems and can provide connectivity with built-in signal conditioning. Fundamental principles of photonic signal processing, including sampling, tuning, and noise, are discussed. Structures that can extend the performance of photonic signal processors are presented, including methods for improving the filter shape characteristics of interference mitigation filters, techniques to increase the stopband attenuation of bandpass filters, and methods to achieve large free spectral range. Several photonic signal processors, including high-resolution microwave filters, widely tunable filters, arbitrary waveform generators, and fast signal correlators, are discussed. Techniques to solve the fundamental noise problem in photonic signal processors are described, and coherence-free structures for few-tap notch filters are discussed. Finally, a new concept for realizing multiple-tap coherence-free processor filters, based on a new frequency-shifting technique, is presented. The structure not only eliminates the phase-induced intensity noise limitation, but can also generate a large number of taps to enable the achievement of processors with high performance and high resolution.
701 citations
TL;DR: The current state of the art with respect to quasi-optical components (low-pass, high-pass and band-pass filters, dichroics and beam-dividers) as developed for the FIR and sub-millimetre wavelength region are reviewed.
Abstract: The Astronomical Instrumentation Group at Cardiff University has been developing metal mesh optical filters for more than 30 years, which are currently in use in many ground-, balloon- and space-based instruments. Here we review the current state of the art with respect to these quasi-optical components (low-pass, high-pass and band-pass filters, dichroics and beam-dividers) as developed for the FIR and sub-millimetre wavelength region.
We compare performance data with various modelling tools (HFSS, transmission line theory or Floquet mode analysis). These models assist with our understanding of the behaviour of these filters when used at non-normal incidence or in the diffraction region of the grid structures. Interesting artefacts, such as the Wood anomalies and behaviour with S and P polarisations, which dictate the usage of these components in polarisation sensitive instruments, will be discussed.
394 citations
TL;DR: In this article, a single-band-pass tunable microwave filter was proposed based on a broadband optical source and a fiber Mach-Zehnder interferometer and showed a high Q factor over a tuning range of 5-17 GHz.
Abstract: The authors present the theoretical analysis and experimental demonstration of a novel single-bandpass tunable microwave filter. The filter is based on a broadband optical source and a fiber Mach-Zehnder interferometer and shows a high Q factor over a tuning range of 5-17 GHz. A generalized analysis considering that the optical signal propagates along optical delay lines with a dispersion slope different from zero is presented.
294 citations
TL;DR: In this paper, an error-free and pattern-independent wavelength conversion at 160 Gb/s was demonstrated using an optical bandpass filter (OBF) placed at the amplifier output.
Abstract: Error-free and pattern-independent wavelength conversion at 160 Gb/s is demonstrated. The wavelength converter utilizes a semiconductor optical amplifier (SOA) with a recovery time greater than 90 ps and an optical bandpass filter (OBF) placed at the amplifier output. This paper shows that an OBF with a central wavelength that is blue shifted compared to the central wavelength of the converted signal shortens the recovery time of the wavelength converter to 3 ps. The wavelength converter is constructed by using commercially available fiber-pigtailed components. It has a simple configuration and allows photonic integration.
226 citations
TL;DR: In this article, the authors investigated theoretically and experimentally transmission color filters using silicon subwavelength gratings on quartz substrates, and obtained transmission spectrum obtained from a coupling between an incident light and the submicrometer periodic grating matches with human color perception.
Abstract: We investigate theoretically and experimentally transmission color filters using silicon subwavelength gratings on quartz substrates. Each grating area is 120 mum-square, which is suitable pixel size for displays and multichannel detectors. In the fabrication, electron beam lithography and fast atom beam etching are used. The grating periods are 400, 350, and 440 nm for the red, green, and blue filters, respectively. The transmission spectrum obtained from a coupling between an incident light and the submicrometer periodic grating matches with human color perception. The transmittances of 71.1%, 58.1%, and 59.3% are obtained for the red, green, and blue filters, respectively
192 citations
TL;DR: In this paper, a chirp-managed directly modulated laser (CML) was used for uncompensated 10-Gb/s transmission over >200 km at 1.55 /spl mu/m.
Abstract: We demonstrate a new highly dispersion tolerant modulation format using a chirp-managed directly modulated laser (CML) for uncompensated 10-Gb/s transmission over >200 km at 1.55 /spl mu/m. The CML consists of a distributed feedback (DFB) laser followed by an optical filter. We show that the combination of adiabatic chirp from the DFB and filter edge response produces high extinction ratio pulses with nearly uniform phase, abrupt phase shifts at bit transitions, and a correlation between the 1 bits; 1 bits separated by odd number of 0 bits are /spl pi/ out of phase. This results in carrier suppression, 1/2 the bandwidth of standard nonreturn-to-zero, and high tolerance to positive and negative dispersion.
178 citations
TL;DR: The fabrication of high quality monolithically integrated optical long-pass filters, prepared by incorporating dye molecules directly into the microfluidic chip substrate, thereby providing a fully integrated solution that removes the usual need for discrete optical filters.
Abstract: We report the fabrication of high quality monolithically integrated optical long-pass filters, for use in disposable diagnostic microchips. The filters were prepared by incorporating dye molecules directly into the microfluidic chip substrate, thereby providing a fully integrated solution that removes the usual need for discrete optical filters. In brief, lysochrome dyes were added to a poly(dimethylsiloxane) (PDMS) monomer prior to moulding of the microchip from a structured SU-8 master. Optimum results were obtained using 1 mm layers of PDMS doped with 1200 µg mL−1 Sudan II, which resulted in less than 0.01% transmittance below 500 nm (OD 4), >80% above 570 nm, and negligible autofluorescence. These spectral characteristics compare favourably with commercially available Schott-glass long-pass filters, indicating that high quality optical filters can be straightforwardly integrated into the form of PDMS microfluidic chips. The filters were found to be robust in use, showing only slight degradation after extended illumination and negligible dye leaching after prolonged exposure to aqueous solutions. The provision of low cost high quality integrated filters represents a key step towards the development of high-sensitivity disposable microfluidic devices for point-of-care diagnostics.
164 citations
1 Jan 2006
TL;DR: Optical Filters in Wavelength-Division Multiplex Systems as discussed by the authors, phase characteristics of optical filters, Diffraction Gratings WDM Components, Fibre Bragg Gratments, Fabry-Perot Interferometer Filters, Dielectric Multilayer Filters and Interleavers.
Abstract: Optical Filters in Wavelength-Division Multiplex Systems.- Phase Characteristics of Optical Filters.- Diffraction Gratings WDM Components.- Arrayed Waveguide Gratings.- Fibre Bragg Gratings.- Fabry-Perot Interferometer Filters.- Dielectric Multilayer Filters.- Ring-Resonator-Based Wavelength Filters.- Interleavers.
126 citations
TL;DR: In this paper, a 2R optical regenerator based on self-phase modulation (SPM)-induced spectral broadening followed by optical filtering has been shown to selectively attenuate spontaneous emission noise more than the pulsed signal.
Abstract: We show both theoretically and experimentally that signal re-amplifying and reshaping (2R) optical regenerator based on self-phase-modulation (SPM)-induced spectral broadening followed by optical filtering has significant advantages over conventional 2R regenerators. By discriminating amplified spontaneous emission noise from a pulsed signal, the SPM-based regenerator is able to selectively attenuate noise more than the pulsed signal. This unique feature results in a direct improvement in bit-error ratio (BER) of a noisy pulsed signal, whereas conventional 2R regenerators can only prevent BER degradation-not actually improve it. We compare the two classes of regenerator and highlight their fundamental differences. We also demonstrate the BER improvement of a noisy signal filtered with an SPM-based regenerator that utilizes a highly nonlinear silica fiber, and present a compact version by exploiting a short length of As2Se3 chalcogenide glass fiber
111 citations
TL;DR: In this paper, an incoherent microwave photonic filter with complex coefficients implemented in the optical domain is proposed and demonstrated for the first time to the knowledge, based on a tunable optically induced RF phase-shift that is obtained by means of a novel optical signal processing technique that makes combined use of optical single-sideband modulation and stimulated Brillouin scattering.
Abstract: We propose and demonstrate for the first time to our knowledge an incoherent microwave photonic filter with complex coefficients implemented in the optical domain. The system is based on a tunable optically induced RF phase-shift that is obtained by means of a novel optical signal processing technique that makes combined use of optical single-sideband modulation and stimulated Brillouin scattering. A two-tap filter is built demonstrating full tunability of its frequency response by dynamically changing the phase shift of a complex coefficient
106 citations
TL;DR: In this paper, a generalized approach for determination of transmittance (transfer function) in Z-domain of optical waveguide based ring resonator is introduced, and the simulated results of single and double ring architectures are compared with those of previously published results.
21 May 2006
TL;DR: In this article, a line-by-line pulse shaping control for optical arbitrary waveform generation (O-AWG) is presented, independent manipulation of individual spectral lines from a mode-locked frequency comb leads to synthesis of user-specified ultrafast optical waveforms with unprecedented frequency resolution.
Abstract: We demonstrate line-by-line pulse shaping control for optical arbitrary waveform generation (O-AWG). Independent manipulation of individual spectral lines from a mode-locked frequency comb leads to synthesis of user-specified ultrafast optical waveforms with unprecedented frequency resolution.
5 Mar 2006
TL;DR: square-16-QAM is introduced as a novel candidate for future high-capacity and high spectrally efficient optical systems and an algorithm for square-16 -QAM digital phase estimation is developed, whose performance and limitations are investigated in simulations.
Abstract: The potential for higher spectral efficiency and recent activities in the area of coherent optical systems raise the interest in new multi-level modulation formats for optical transmission. In this paper square-16-QAM is introduced as a novel candidate for future high-capacity and high spectrally efficient optical systems. Different possible transmitters as well as the homodyne IQ-receiver are illustrated. At the transmitter side the implementation of an electrical level-generator is shown experimentally. At the receiver side options for the realization of the optical 2/spl times/4 90 /spl deg/-hybrid are discussed. Furthermore, an algorithm for square-16-QAM digital phase estimation is developed, whose performance and limitations are investigated in simulations.
Patent•
27 Nov 2006
TL;DR: In this paper, a multivariate optical computing and analysis system is presented, which includes transmitting a first light from a light source, generating a second light by reflecting the first light, and directing a portion of the second light with a beamsplitter.
Abstract: A method of arranging and utilizing a multivariate optical computing and analysis system includes transmitting a first light from a light source; generating a second light by reflecting the first light from the sample; directing a portion of the second light with a beamsplitter; and arranging an optical filter mechanism in a normal incidence orientation to receive the portion of the second light, the optical filter mechanism being configured to optically filter data carried by the portion of the second light.
Patent•
27 Nov 2006TL;DR: In this paper, a multivariate optical computing and analysis system is presented, which includes a light source configured to radiate a first light along a first ray path, a modulator disposed in the first-ray path, the modulator configured to modulate the first light to a desired frequency, a spectral element disposed proximate the modulators, the spectral element configured to filter the firstlight for a spectral range of interest of a sample; a cavity disposed in communication with the cavity, the cavity configured to direct the first beacon in a direction of the sample, a tube disposed
Abstract: A multivariate optical computing and analysis system includes a light source configured to radiate a first light along a first ray path; a modulator disposed in the first ray path, the modulator configured to modulate the first light to a desired frequency; a spectral element disposed proximate the modulator, the spectral element configured to filter the first light for a spectral range of interest of a sample; a cavity disposed in communication with the spectral element, the cavity configured to direct the first light in a direction of the sample; a tube disposed proximate the cavity, the tube configured to receive and direct a second light generated by a reflection of the first light from the sample, the tube being further configured to separate the first and second lights; a beamsplitter configured to split the second light into a first beam and a second beam; an optical filter mechanism disposed to receive the first beam, the optical filter mechanism configured to optically filter data carried by the first beam into at least one orthogonal component of the first beam; and a detector mechanism in communication with the optical filter mechanism to measure a property of the orthogonal component to measure the data.
TL;DR: In this article, the authors used the Navy Prototype Optical Interferometer equipped with custom-made narrowband filters to obtain the highest spatial resolution measurements of the H -emitting regions of Be stars obtained to date.
Abstract: : Interferometric observations of two well-known Be stars, gamma Cas and phi Per, were collected and analyzed to determine the spatial characteristics of their circumstellar regions. The observations were obtained using the Navy Prototype Optical Interferometer equipped with custom-made narrowband filters. The filters isolate the H(alpha) emission line from the nearby continuum radiation, which results in an increased contrast between the interferometric signature due to the H(alpha)-emitting circumstellar region and the central star. Because the narrowband filters do not significantly attenuate the continuum radiation at wavelengths 50 nm or more away from the line, the interferometric signal in the H(alpha) channel is calibrated with respect to the continuum channels. The observations used in this study represent the highest spatial resolution measurements of the H -emitting regions of Be stars obtained to date. These observations allow us to demonstrate for the first time that the intensity distribution in the circumstellar region of a Be star cannot be represented by uniform disk or ringlike structures, whereas a Gaussian intensity distribution appears to be fully consistent with our observations.
TL;DR: In this paper, a special section devoted to optical signal processing is devoted to waveform generation, coherent photonic processing, A/D conversion, spatially resolved detection, active optical filters, high spatial resolution and boundless-range optics.
Abstract: The twenty-seven papers in this special section are devoted to optical signal processing. Some of the topics covered include: waveform generation; coherent photonic processing; A/D conversion; spatially resolved detection; active optical filters; high spatial resolution; and boundless-range optics.
Patent•
27 Jul 2006
TL;DR: In this paper, the authors proposed a frequency domain optical coherence imaging system with an optical source, an optical detector and an optical transmission path between the optical source and the optical detector.
Abstract: Frequency domain optical coherence imaging systems have an optical source, an optical detector and an optical transmission path between the optical source and the optical detector The optical transmission path between the optical source and the optical detector reduces an effective linewidth of the imaging system The optical source may be a broadband source and the optical transmission path may include a periodic optical filter
TL;DR: In this paper, a radially variable interference filter is proposed that can maintain acceptable efficiency over its entire surface in solar concentrating systems with a wide field of view, by applying ray tracing methods and a mapping technique, the angle at which the greatest proportion of energy is incident can be determined at a function of position on the filter surface.
Patent•
7 Nov 2006
TL;DR: In this article, an optical image measuring instrument capable of shorting the measurement time is presented. But the measurement of the object is performed using two polarized components (L1, L2) of the interference light.
Abstract: An optical image measuring instrument capable of shorting the measurement time. A flash is outputted from a xenon lamp (2) and converted into a wide-band light by means of an optical filter (2A). The flash is converted into a linearly polarized light by means of a polarizing plate (3). The linearly polarized light is divided into a signal light (S) and a reference light (R) by means of a semitransparent mirror (6). The reference light (R) is converted into a circularly polarized light by means of a wavelength plate (7). The signal light (S) and the reference light (R) are combined by means of a semitransparent mirror (6) to produce an interference light (L). A CCD (23) detects the interference light having the same characteristic as the interference light (L). The interference light (L) is separated into an S-polarized component (L1) and a P-polarized component (L2) by means of a polarized beam splitter (11). These components are detected by means of CCDs (21, 22). A computer (30) creates an image of an object (O) to be measured from the detection signals from the CCDs (21, 22, 23). With such an optical image measuring instrument (1), since two polarized components (L1, L2) of the interference light (L) can be simultaneously obtained, the measurement time can be shortened.
TL;DR: In this paper, a simple model that accounts for the parasitic effect of silicon to near-infrared light was proposed and solved for frequencies up to 100kHz and for laser wavelengths between 750 and 1064nm.
Abstract: In a typical optical tweezers detection system, the position of a trapped object is determined from laser light impinging on a quadrant photodiode. When the laser is infrared and the photodiode is of silicon, they can act together as an unintended low-pass filter. This parasitic effect is due to the high transparency of silicon to near-infrared light. A simple model that accounts for this phenomenon [Berg-Sorensen et al., J. Appl. Phys. 93, 3167 (2003)] is here solved for frequencies up to 100kHz and for laser wavelengths between 750 and 1064nm. The solution is applied to experimental data in the same range, and is demonstrated to give this detection system of optical tweezers a bandwidth, accuracy, and precision that are limited only by the data acquisition board’s bandwidth and bandpass ripples, here 96.7kHz and 0.005dB, respectively.
TL;DR: In this paper, a type of guided-mode resonance (GMR) reflection filter incorporating multimode resonance and the Brewster effect is presented, and the effect index is calculated using the zero-order permittivity e0,TM of the effective media theory.
Abstract: In this letter, a type of guided-mode resonance (GMR) reflection filter incorporating multimode resonance and the Brewster effect is presented. Long-range, low sidebands, and multiple channels are found to be obtainable for a single-layer GMR reflection filter with a TM-polarized plane wave incident at the Brewster angle. Detailed characteristics are calculated using rigorous coupled-wave analysis. In our calculation, for TM-polarized incident wave, we find it sufficiently accurate to calculate the effect index by using the zero-order permittivity e0,TM of the effective media theory, and narrowband multichannel reflectance can be achieved at the Brewster angle by tuning the grating depth.
TL;DR: One-dimensional photonic-crystal reflectance filters operating in the near-ultraviolet wavelengths were fabricated using nanoreplica molding from a silicon surface structure template, patterned using electron-beam lithography.
Abstract: One-dimensional photonic-crystal reflectance filters operating in the near-ultraviolet wavelengths were fabricated using nanoreplica molding from a silicon surface structure “master” template, patterned using electron-beam lithography. The fabricated devices produce a narrow linewidth reflectance resonance at a wavelength of 411nm for TM polarized illumination and a broadband reflectance characteristic between 402 and 439nm for TE polarized illumination. The measured reflectance spectra are accurately predicted by Rigorous Coupled Wave Analysis computer simulations, which demonstrate the capability for designing similar filter performance for wavelengths <350nm through minor adjustment of the photonic-crystal lattice period.
TL;DR: By using Rb vapor filters, free-space quantum key distribution with the B92 protocol was realized experimentally; the filters based on the Faraday anomalous dispersion effect were used to suppress strong background light.
Abstract: By using Rb vapor filters, free-space quantum key distribution with the B92 protocol was realized experimentally; the filters based on the Faraday anomalous dispersion effect were used to suppress strong background light. With these atomic filters as spectral filtering, average transmission rates of sifted keys and corrected keys have reached as high as 3.14 and 1.56kbits∕s, respectively, while the error rate was maintained at a reasonable low level of 5.10%. The experimental results show that our Rb vapor filters with transmission efficiency of around 60% operate well under the condition of the mean photon number n¯⩽0.1.
TL;DR: First-characterization results indicate that these types of filter may exhibit higher laser-induced damage-threshold values than those of classical filters.
Abstract: Methods for the manufacture of rugate filters by the ion-beam-sputtering process are presented. The first approach gives an example of a digitized version of a continuous-layer notch filter. This method allows the comparison of the basic theory of interference coatings containing thin layers with practical results. For the other methods, a movable zone target is employed to fabricate graded and gradual rugate filters. The examples demonstrate the potential of broadband optical monitoring in conjunction with the ion-beam-sputtering process. First-characterization results indicate that these types of filter may exhibit higher laser-induced damage-threshold values than those of classical filters.
TL;DR: Computer simulation results obtained with the proposed adaptive filter in test scenes are discussed and compared with those of various correlation filters in terms of discrimination capability, tolerance to input additive noise that is always present in image sensors, and to small geometric image distortions.
Abstract: New adaptive correlation filters based on a conventional synthetic discriminant function (SDF) for reliable recognition of an object in cluttered background are proposed. The information about an object to be recognized, false objects, and a background to be rejected is utilized in an iterative training procedure to design a correlation filter with a given value of discrimination capability. Computer simulation results obtained with the proposed adaptive filter in test scenes are discussed and compared with those of various correlation filters in terms of discrimination capability, tolerance to input additive noise that is always present in image sensors, and to small geometric image distortions.
Patent•
25 Jul 2006
TL;DR: In this article, a splitter and a combiner are configured to combine at least a portion of the split input spectrum into a single output port, splitter having respective first and second input and output ports, and a respective transfer matrix, the matrix of the combiner being the diagonal transpose of that of the splitter.
Abstract: Optical devices extending the free spectral range and tunability of, and enabling hitless switching of, integrated optical filters suitable for add-drop filters. Devices include (i) a splitter device configured to split an input spectrum among a plurality of output ports, and a combiner device configured to combine at least a portion of the split input spectrum into a single output port, splitter and combiner having respective first and second input and output ports, and a respective transfer matrix, the matrix of the combiner being the diagonal transpose of that of the splitter; (ii) a first optical path coupling the first output port of the splitter and the first input port of the combiner; (iii) a second optical path coupling the second output port of the splitter and the second input port of the combiner, wherein the first and second optical paths are configured to introduce, at least at a wavelength of the input spectrum, a relative phase shift of π radians; and (iv) an optical filter coupled to at least one of the first and second optical paths.
TL;DR: In this article, double lock-in detection is applied to both a probe and a pump wave at different frequencies to effectively remove the noise induced by the backward reflection of the pump waves, and the SSB modulator is used to purify the probe wave by suppressing the other first order sideband component.
Abstract: We demonstrate a novel technique to enlarge the measurement range of a correlation-based fiber Brillouin distributed sensing system using double lock-in amplifiers and a single-sideband (SSB) modulator. In our work, the lock-in detection is applied to both a probe and a pump waves at different frequencies to effectively remove the noise induced by the backward reflection of the pump waves, and the SSB modulator is used to purify the probe wave by suppressing the other first-order sideband component. A 300-m measurement range with a 20-cm spatial resolution is achieved successfully without any optical filter
TL;DR: In this article, a coherent optical signal processing approach for synthesis of programmable microwave amplitude filters over an ultrawideband was presented, which allows direct synthesis of microwave filter functions in spectral domain without computing filter coefficients, which is needed for a discrete-time-domain approach.
Abstract: This paper presents a novel coherent optical signal processing approach for synthesis of programmable microwave amplitude filters over an ultrawideband. The authors' scheme relies on a programmable hyperfine optical filter implemented in a pulse-shaping geometry, which provides arbitrary, user-defined amplitude-filtering functions over a 50-GHz bandwidth with resolution better than 0.7 GHz. In contrast to previous work on discrete time optical processing of microwave signals, their approach allows direct synthesis of microwave filter functions in spectral domain without computing filter coefficients, which is needed for a discrete-time-domain approach.
TL;DR: In this article, the authors proposed novel ultrafast and polarization-independent all-optical analog-to-digital conversion schemes, which are realized by filtering the broadened and split spectrum induced by the soliton effect or self-phase modulation in fiber with an arrayed waveguide grating.
Abstract: The Kerr effect in fiber is expected to play a major role in ultrafast all-optical signal processing, which can overcome the obstacles of inherently limited operating speed of electronic devices. In this paper, we propose novel ultrafast and polarization-independent all-optical analog-to-digital conversion schemes. The proposed schemes are realized by filtering the broadened and split spectrum induced by the soliton effect or self-phase modulation in fiber with an arrayed waveguide grating. We conducted proof-of-principle experiments and successfully demonstrated two-bit all-optical analog-to-digital conversions with Gray code output, which shows the feasibility of the proposed scheme.