Showing papers on "Extinction ratio published in 1986"
TL;DR: In this article, a strictly nonlocking 8×8 integrated optics switch matrix in Ti: LiNbO3 was presented, which consisted of 64 directional couplers on one chip.
Abstract: We report on a strictly nonlocking 8×8 integrated optics switch matrix in Ti: LiNbO3. The matrix comprises 64 directional couplers on one chip. Insertion losses less than 7 dB have been measured. The extinction ratio has an average value of 30.5 dB for the directional couplers.
107 citations
TL;DR: In this article, an electroabsorption (EA) light modulator (LM) with a strip-loaded GaInAsP planar waveguide has been described, and a 3dB bandwidth of 3.8 GHz has been achieved and a pulse modulation operation under 2 Gbit/s nonreturn-to-zero (NRZ) pseudorandom pattern has also been confirmed.
Abstract: We describe fabrication and characterization of an electroabsorption (EA) light modulator (LM) with a strip-loaded GaInAsP planar waveguide. The EA LM's were fabricated from hydride vapor-phase-epitaxy (VPE) grown wafers. The electroabsorption, the insertion loss, the electrical properties, and the modulation characteristics were investigated for the EA LM's. The drive voltage at a 99-percent modulation depth has been noticeably reduced to 4.5 V by optimizing the thicknesses of the epitaxial layers. The total capacitance of 1.5 pF was obtained by inserting an insulating film under the wire-bonding pad and by improving the mount design. Consequently, a 3-dB bandwidth of 3.8 GHz has been achieved and a pulse modulation operation under 2 Gbit/s nonreturn-to-zero (NRZ) pseudorandom pattern has also been confirmed. Moreover, the dynamic spectra of the EA modulators were measured for the first time. A spectral broadening factor α has been determined to be 1-4 from a relative strength of the sideband to the carrier and it has been experimentally found to decrease with increasing the electric field inside the absorptive waveguide. As the other measures of merit for the EA LM's, the extinction ratio over 23 dB and the insertion loss of 10-14 dB including a coupling loss due to an end-fire method were obtained. As a whole, these results have exhibited that the EA LM is a promising external modulator which will be monolithically integrated into a gigabit per second optical source with a dynamic single-mode laser.
88 citations
TL;DR: In this paper, the operation and design considerations for a general class of symmetric directional coupler switches are discussed in terms of asymmetries, and comparative results between various waveguide and electrode geometries are made.
Abstract: Operation and design considerations are described for a general class of symmetric directional coupler switches. Performance limitations are discussed in terms of asymmetries. Comparisons are made between various waveguide and electrode geometries. Measured devices operating at \lambda = 0.83 \mu m have a V π voltage length product under 30 V mm and an extinction ratio greater than 28 dB in each output state.
82 citations
TL;DR: A novel low-loss electro-optic Ti–LiNbO3 TE–TM mode converter is demonstrated and is made immune from the optical damage and Li2O outdiffusion problems typically associated with LiNb O3 devices by the use of a z-propagation waveguide.
Abstract: A novel low-loss electro-optic Ti–LiNbO3 TE–TM mode converter is demonstrated. The polarization conversion is not wavelength selective. Extremely high conversion efficiency with an extinction ratio of more than 33 dB has been achieved with 7-V drive. The device is made immune from the optical damage and Li2O outdiffusion problems typically associated with LiNbO3 devices by the use of a z-propagation waveguide.
63 citations
TL;DR: In this paper, a Niobate traveling-wave interferometric light modulator/switch with a groove excavated at the electrode gap has been fabricated and tested at microwave frequency.
Abstract: A Ti dffused lithium niobate traveling-wave interferometric light modulator/switch with a groove excavated at the electrode gap has been fabricated and tested at microwave frequency. The groove suppresses the undesirable light coupling between the two parallel waveguides for the phase shifting section so that the drive voltage is decreased by reducing the separation of the parallel waveguides, or of the electrodes. In addition, the groove decreases the effective index for the modulating wave to reduce the velocity mismatch between light wave and microwave so that the bandwidth is broadened. The modulation experiment was carried out from dc to 15 GHz at 633 nm light wavelength. For the modulator with the electrodes 6 mm long and 10 μm apart, the half-wave or switching voltage was 3 V, the extinction ratio was 18 dB, the 3 dB bandwidth was 12 GHz and a P/\Delta f of 1.5 mW/GHz was obtained.
61 citations
TL;DR: A metal-clad fiber-optic cutoff polarizer using a thin film is proposed and fabricated and an extinction ratio of 47 dB with excess loss of 1 dB in the polarizer has been achieved.
Abstract: A metal-clad fiber-optic cutoff polarizer using a thin film is proposed and fabricated. An extinction ratio of 47 dB with excess loss of 1 dB in the polarizer has been achieved.
55 citations
TL;DR: In this paper, continuous metal/glass fiber polarisers incorporating Ga or In/Sn alloy have been fabricated and an extinction ratio of greater than 37dB with an insertion loss of less than 1 dB can be obtained over a 250nm spectral window around 1300nm.
Abstract: Continuous metal/glass fibre polarisers incorporating Ga or In/Sn alloy have been fabricated. An extinction ratio of greater than 37dB with an insertion loss of less than 1 dB can be obtained over a 250nm spectral window around 1300nm. Extinction ratios as high as 52dB have been measured at 830 nm.
42 citations
TL;DR: In this paper, a large on/off ratio optical modulation of long-wavelength light propagating along the plane of InGaAs/InAlAs multiple-quantum-well (MQW) structures grown by molecular beam epitaxy (MBE) is obtained for the first time.
Abstract: Large on/off ratio optical modulation of long-wavelength light propagating along the plane of InGaAs/InAlAs multiple-quantum-well (MQW) structures grown by molecular beam epitaxy (MBE) is obtained for the first time. These waveguide MQW optical modulators have a modulation on/off ratio of 30:1 (15 dB) at a driving voltage as low as 9 V, and a capacitance-limited pulse response of 280 ps (FWHM). This measurement is the first step in achieving faster and higher extinction ratio devices.
31 citations
TL;DR: A directional coupler optical switch with good switching characteristics and low-loss guiding properties and high speed operation of 1.6 GHz was achieved.
Abstract: A directional coupler optical switch with good switching characteristics (extinction ratio of more than 22 dB at 22.5-V applied voltage) and low-loss guiding properties (total insertion loss of 10.7 dB including Fresnel reflection loss of 4.0 dB) has been developed. The switch element was mounted on a ceramic stem and jointed directly with polarization-maintaining optical fibers. High speed operation of 1.6 GHz was achieved.
30 citations
TL;DR: In this paper, random fluctuations in the local Ti concentration profiles of Ti-diffused LiNbO 3 waveguides have been observed, and these variations explain the degraded switch extinction ratio (i.e., crosstalk) and other nonideal characteristics observed in Li NbO3 optical switches.
Abstract: We have observed random fluctuations in the local Ti concentration profiles of Ti-diffused LiNbO 3 waveguides. Calculations show that these variations explain the degraded switch extinction ratio (i.e., crosstalk) and other nonideal characteristics observed in LiNbO 3 optical switches. We also demonstrate by calculation a new device configuration for eliminating this source of crosstalk.
29 citations
TL;DR: In this paper, an electrooptic leaky anisotropic waveguide using a nematic liquid crystal overlayer was proposed for lowvoltage driving, and demonstrated its fundamental operation at 0.63 μm.
Abstract: In this paper we propose an electrooptic leaky anisotropic waveguide using a nematic liquid crystal overlayer for low-voltage driving, and demonstrate its fundamental operation at 0.63 μm. The peak-to-peak voltage required to obtain 20-dB extinction ratio was only 4 V, which was about one-tenth of that of the waveguide previously reported. Switching speeds of millisecond order are demonstrated.
TL;DR: The temperature characteristics of Faraday rotator material Y3xGd3(1−x)Fe5O12 are discussed and the material with YIG molar fraction x between 0.57 and 0.7 has a small temperature coefficient of the Faraday rotation and is suitable for isolators with temperature-stable isolation.
Abstract: The temperature characteristics of Faraday rotator material Y3xGd3(1−x)Fe5O12 are discussed. The material with YIG molar fraction x between 0.57 and 0.7 has a small temperature coefficient of the Faraday rotation and is suitable for isolators with temperature-stable isolation. The extinction ratio of the Faraday rotator can be minimized by selecting an appropriate polarization direction of light incident on it. This polarization direction should also be selected by taking the temperature dependence into account. Isolators using the material as a rotator hold isolation to >40 dB throughout the temperature range from 0 to 50°C.
TL;DR: In this article, a distributed feedback laser diode (DFB-LD) module for single-mode fiber coupling is described in the 1.5-μm wavelength region, and an optical isolator is constructed in the two lens coupling circuit to stabilize the DFB-LD characteristics.
Abstract: A distributed feedback laser diode (DFB-LD) module for single-mode fiber coupling is described in the 1.5-μm wavelength region. An optical isolator is constructed in the two lens coupling circuit to stabilize the DFB-LD characteristics. It consists of a DFB-LD as a polarizer, a yttrium iron garnet (YIG) plate and an analyzer. Coupling characteristics and attainable isolation of the proposed circuit have been studied theoretically and experimentally. The effect of reflected light on the DFB-LD characteristics such as relative intensity noise (RIN) and oscillation spectrum has been experimentally investigated taking into account the polarization of the reflected light. It has been clarified that the DFB-LD can function as an effective polarizer with an extinction ratio of more than 20 dB. The DFB-LD module was successfully fabricated to have stable spectrum characteristics and to sufficiently suppress the noise caused by reflections. It has been confirmed by a long haul transmission experiment that this module is applicable to large capacity optical fiber transmission systems.
TL;DR: In this article, the effect of high optical power levels, at a wavelength of 1.51 μn, on the characteristics of LiNbO3 Mach-Zehnder waveguide modulators is reported.
Abstract: A study of the effect of high optical power levels, at a wavelength of 1.51 μn, on the characteristics of LiNbO3 Mach—Zehnder waveguide modulators is reported. It is shown that the important modulator parameters, i.e. optical phase bias, extinction ratio, insertion loss and switching voltage, are stable for waveguide powers of <75 mW.
TL;DR: In this article, thin-film polarisers using a dielectric buffer layer and a metallic overlay on Ti:LiNbO3 channel waveguides for λ = 1.3 μm have been designed and fabricated.
Abstract: Thin-film polarisers using a dielectric buffer layer and a metallic overlay on Ti:LiNbO3 channel waveguides for λ = 1.3 μm have been designed and fabricated. The TM mode extinction ratio better than 35 dB and negligible TE mode excess losses have been measured with Si3N4/Al polarisers 2 mm long.
TL;DR: In this paper, a PANDA-fibre wavelength-selective region, fiberoptic polarising beam splitter and fiber polarisers, is demonstrated at 1.53 μm.
Abstract: A new all-PANDA-fibre multi/demultiplexer, which consists of 1.65 m PANDA-fibre wavelength-selective region, fibreoptic polarising beam splitter and fibre polarisers, is demonstrated at 1.53 μm. To show the feasibility of the fibre-optic multi/demultiplexer in wavelength-division multiplexing (WDM), two different spectral components of the multimode laser (δλ = 13.8 A) were successfully separated, with an extinction ratio of 23 dB and an insertion loss of 1.5 dB.
TL;DR: In this paper, an all-fibre-optic-logic AND gate is demonstrated, which consists of a birefringent fiber, a coiled fibre used as a quarter-wave plate, and a highly bireringent fibre as a polariser.
Abstract: Operation of an all-fibre-optic-logic AND gate is demonstrated The logic gate consists of a birefringent fibre, a coiled fibre used as a quarter-wave plate, and a highly birefringent fibre as a polariser The 9 dB extinction ratio of ‘on’ and ‘off’ states is achieved for the all-fibre-type AND gate
TL;DR: In this paper, a spectral bandpass filter with 17 nm FWHM (full width at half-maximum) and a bandelimination filter with -60.8 dB extinction ratio have been realized.
Abstract: Fibre-optic spectral filters using concatenated dual-core fibres are reported. Both a spectral bandpass filter with 17 nm FWHM (full width at half-maximum) and a band-elimination filter with -60.8 dB extinction ratio have been realised.
Patent•
08 Apr 1986
TL;DR: In this article, a bias current is applied to a semiconductor laser to emit a laser light having excellent extinction ratio by controlling the bias current applied when the light of the laser is extinguished on the basis of a threshold bias current value.
Abstract: PURPOSE:To emit a laser light having excellent extinction ratio by controlling a bias current applied when the light of a semiconductor laser is extinguished on the basis of a threshold bias current value and applying the bias current of the degree not laser oscillating near the threshold value to the laser. CONSTITUTION:When a controller 5 calculates nonlight emitting bias current value IBIAS, it is applied to a semiconductor laser 1. The controller 5 feeds data for increasing a light emitting current to a latch 8 until a predetermined emitted light quantity is obtained. The controller 5 holds the value at the latch 8 and instructs a laser OFF signal to a switching circuit 3. Thus, only the value IBIAS is applied to the laser 1 to become capable of printing. It becomes possible to print by the above operation, the controller 5 then generates a laser ON signal LON on the basis of a print signal, and the laser 1 emits a light in response to the input print signal on the basis of the current in which a light emitting current is added to the bias current.
15 May 1986
TL;DR: In this article, a wideband lasercom transmitter based on dichroic combination of directly modulatedGaAlAs laser beams was built and its performance with regard to various requirements was evaluated; these include rise and fall times, extinction ratio, modulation bandwidth, wave-length stability, power, polarization, and transverse mode structure.
Abstract: Wideband Lasercour Transmitter PerformanceRobert J. SmithDepartment of Electro- Optics, McDonnell Douglas Astronautics Co.Bldg. IOTA, Area 231, P.O. Box 516, St. Louis, Missouri 63166AbstractA Wideband Lasercom Transmitter based on dichroic combination of directly modulatedGaAlAs laser beams was built, and its performance with regard to various requirements wasevaluated; these include rise and fall times, extinction ratio, modulation bandwidth, wave-length stability, power, polarization, and transverse mode structure.IntroductionSuccessful dichroic combination of beams from several independent lasers for the purposeof increased radiance depends heavily on the spectral characteristics of the individual
TL;DR: In this article, a GaAs/AlGaAs directional coupler switch for the first time with a device length shorter than 1 mm was fabricated by utilising the good controllability of molecular beam epitaxy and reactive ion beam etching.
Abstract: A GaAs/AlGaAs directional coupler switch, for the first time with a device length shorter than 1 mm, has been fabricated by utilising the good controllability of molecular beam epitaxy and reactive ion beam etching. The switching voltage is as low as 5V. The extinction ratio is 17dB for a crossover state and 14dB for a straight-through state.
TL;DR: An ultrahigh extinction ratio has been achieved by using a Ti-indiffused Y-cut LiNbO(3) cutoff modulator with a 165-V drive at a wavelength of 0.6328 microm.
Abstract: A new type of cutoff light modulator, which consists of a single-mode channel waveguide and strip electrodes placed asymmetrically on either side of the guide, is proposed. When a voltage is applied to the electrodes, this device exhibits an asymmetric refractive-index profile along a direction parallel to the crystal surface through the electrooptic effect. This produces a strong condition for cutoff of the fundamental mode of the guide. An ultrahigh extinction ratio of greater than 56 dB has been achieved by using a Ti-indiffused Y-cut LiNbO(3) cutoff modulator with a 165-V drive at a wavelength of 0.6328 microm.
TL;DR: In this paper, an optical rotator with high-birefringence fiber pigtails containing an in-line tapered fiber polariser was fabricated for use at 1.32 µm.
Abstract: An optical isolator for use at 1.32 μm has been fabricated using standard communication-grade single-mode fibre as an optical rotator fitted with high-birefringence fibre pigtails containing an in-line tapered fibre polariser. A novel adjustment procedure ensures isolation levels are limited only by the polariser extinction ratio. Isolation levels in excess of 21 dB have been recorded with an insertion loss of less than 3 dB.
Patent•
10 Jun 1986
TL;DR: In this article, a light beam from a light source passes through a beam splitter 2 and a polarizer 3 and made incident on one end of an optical fiber 12 of a branch coupler 11, a part thereof passes through ground surface 16, a transparent solid layer 18 and a ground surface 17 and branches to other optical fiber 13, and also a part is propagated to the other end of the optical fiber 14.
Abstract: PURPOSE:To obtain an optical fiber gyroscope having a small drift and a high reliability, by constituting an optical fiber branch coupler so that a polished surface of two pieces of optical fibers which have been bent each other is solidified and joined by a transparent solid layer CONSTITUTION:A light beam from a light source 1 passes through a beam splitter 2 and a polarizer 3 and made incident on one end of an optical fiber 12 of an optical fiber branch coupler 11, a part thereof passes through a ground surface 16, a transparent solid layer 18 and a ground surface 17 and branches to other optical fiber 13, and also, a part is propagated to the other end of the optical fiber 12 In this case, since the transparent solid layer 18 is used, propagation light beams which have been made to branch into two directions are made incident on both ends of an optical fiber loop 5 with stable optical power and extinction ratio Subsequently, said beams pass through a phase modulator 6, go round to the right and left and propagated, and thereafter, coupled by the branch coupler 11 again and each a photodetector 7, and when a signal obtained from the photodetector 7 is brought to a synchronizing amplification synchronously with an AC voltage for driving the phase modulator 6, a rotation detecting output of a small drift is obtained
Patent•
12 Aug 1986
TL;DR: In this article, a magneto-optical crystal having a large angle of Faraday rotation, a small power loss and a high extinction ratio was obtained by epitaxially growing rare earth element-iron garnet contg. in a liq. phase.
Abstract: PURPOSE:To obtain a magneto-optical crystal having a large angle of Faraday rotation, a small power loss and a high extinction ratio by epitaxially growing rare earth element-iron garnet contg. Bi substituted for part of Lu3Fe5O12 at a low temp. in a liq. phase. CONSTITUTION:A mganeto-optical element of a magnetic garnet crystal having a composition represented by a formula BixLu3-xO12(1.0<=x<=3.0) is formed on a garnet crystal substrate of Gd3Ga5O12 by liq. phase epitaxial growth. The garnet crystal substrate may be made of Sm3Fe5O12 or Ca-Mg-Zr substituted Gd3Ga5O12. A melt to be used is a mixture of Bi2O3 with PbO, B2O3, Fe2O3 and Lu2O3, and the molar ratio of (PbO+Bi2O3):B2O3 is regulated to (1-30):1. A magneto-optical crystal having a large angle of Faraday rotation, a small power loss and a high extinction ratio is produced.
TL;DR: In this article, the authors derived the experimental dependence of the power penalty at the receiver against extinction ratio at 180 and 417 Mbit/s NRZ data rates for an optical fiber transmission experiment in which a Ti: LiNbO3 directional coupler was used to externally modulate a multilongitudinal-mode laser.
Abstract: We report bit error rate (BER) measurements, as a function of the extinction ratio, for an optical fibre transmission experiment in which a Ti: LiNbO3 directional coupler was used to externally modulate a 1.3 ?m multilongitudinal-mode laser. We derive the experimental dependence of the power penalty at the receiver against extinction ratio at 180 and 417 Mbit/s NRZ data rates. We also show that a simple BER probabilistic calculation provides good agreement with our experimental data. Finally, we consider the use of polarisation-maintaining fibre as a means of ensuring a stable input polarisation.
01 Jan 1986
TL;DR: In this article, a continuous composite metal/glass singlemode fiber polariser with an extinction ratio greater than 48dB with insertion loss of less than 1dB at 830nm was fabricated.
Abstract: Continuous composite metal/glass single-mode fibre polarisers have been fabricated. The devices exhibit an extinction ratio greater than 48dB with an insertion loss of less than 1dB at 830nm. Moreover, an extinction ratio of more than 40dB can be obtained over a 250nm spectral window ~1300nm.
01 Jan 1986
TL;DR: In this paper, the design, fabrication, and reflectance measurements of a multilayer silver/silicon reflector for use at 584 nm were investigated, and the results indicated that reflectors in the extreme ultraviolet do not perform as well as predicted due to the presence of surface oxides and other surface contamination layers.
Abstract: We have investigated the design, fabrication, and reflectance measurements of a multilayer silver/silicon reflector for use at 584 nm Our results indicate that reflectors in the extreme ultraviolet do not perform as well as predicted due to the presence of surface oxides and other surface contamination layers In addition, we have found that the correct optical constants for silver have now been published We find also that these multilayer coatings can be utilized as reflective polarizers in the EUV with an extinction ratio of 75:1 and a throughput of 28% for the s‐polarized component of the beam
Patent•
21 Jun 1986
TL;DR: In this article, the extinction ratio of a constant polarization fiber was measured by taking out a light polarized in a certain direction from the light discharged from a single mode fiber and receiving the taken-out light by a fiber which has a function to eliminate the clad mode.
Abstract: PURPOSE:To measure accurately an extinction ratio of a constant polarization fiber by taking out a light polarized in a certain direction from the light discharged from a single mode fiber and receiving the taken-out light by a fiber which has a function to eliminate the clad mode CONSTITUTION:The light discharged from a single mode fiber 1 is converted to a parallel light by a lens 2 and is projected to an analyzer 3 Only a certain polarized component is taken out by the analyzer 3 and is condensed by a lens 4 and is received by a light receiving fiber 6 This fiber 6 has a mode field diameter smaller than that of the fiber 1 and has a function to eliminate the clad mode Consequently, the light propagated in a part other than the mode field part of the fiber 1 is not made incident on the mode field part of the fiber 6 Thus, a power meter provided in the exit of the fiber 6 can measure the optical power of only the fundamental mode light of the fiber 1
TL;DR: In this article, the influence of the bias level and nonlinear gain on the achievable minimum output pulse width due to laser chirping was considered, and it was shown that a bias level of about 30% of the optical pulse amplitude yields a two-fold to three-fold increase in the possible bit rate than without bias level.
Abstract: The influence of the bias level and the nonlinear gain on the achievable minimum output pulse width due to laser chirping is considered. Using Gaussian input pulses a bias level of about 30% of the optical pulse amplitude yields a two-fold to three-fold increase in the possible bit rate than without bias level.