Showing papers on "Extinction ratio published in 1984"
TL;DR: In this paper, a traveling-wave Ti-indiffused LiNbO3 guided-wave Mach-Zehnder interferometric modulator has been fabricated and characterized at λ=0.85 μm.
Abstract: A traveling‐wave Ti‐indiffused LiNbO3 guided‐wave Mach–Zehnder interferometric modulator has been fabricated and characterized at λ=0.85 μm. The modulator achieves the theoretical 3‐dB linear small‐signal bandwidth limit of 16 GHz for a 4‐mm‐long interaction length. With a ±2.25‐V drive signal, an extinction ratio of 22 dB is achieved. Linear small‐signal measurements made with a swept‐frequency technique are compared to previously reported measurements.
63 citations
TL;DR: In this article, unequal coupling of an input wave to the even and the odd mode of the coupling region gives rise to another kind of cross-talk, and the extinction ratio is well approximated by the overlap integral of the fields in the two waveguides.
Abstract: Cross‐talk in optical directional couplers is usually considered to be limited only by the processing technology. We show that unequal coupling of an input wave to the even and the odd mode of the coupling region gives rise to another kind of cross‐talk. The extinction ratio is well approximated by the overlap integral of the fields in the two waveguides. For a given coupling length, the higher the index step a waveguide has, the less the cross‐talk is. For straight couplers without bends one way to eliminate the cross‐talk is to offset the input wave relative to the coupled guides with the penalty of power loss. A three‐waveguide coupler has a different cross‐talk problem of comparable magnitude.
55 citations
TL;DR: In this article, a PANDA-fibre gyroscope with a 3 dB coupler and a 43 dB extinction ratio was reported. But the insertion loss was smaller than 0.04 dB when the fiber was bent by the radius R = 10 cm.
Abstract: A new all-PANDA-fibre gyroscope is reported. All components such as the coil, the phase modulator, the 3 dB coupler and the polariser were constructed by the PANDA fibres. The extinction ratio of the fibre-type polariser was 43 dB, with the insertion loss smaller than 0.04 dB when the fibre was bent by the radius R = 10 cm. For long-term behaviour, the peak-to-peak fluctuation of 0.5 deg/h was observed with 40 s integration time
43 citations
TL;DR: In this article, the fundamental mode in highly birefringent fibres is not plane-polarized, as is normally assumed, but has significant orthogonal field components.
Abstract: Experimental results are presented which show that the fundamental mode in highly birefringent fibres is not plane-polarised, as is normally assumed, but has significant orthogonal field components. These components limit the maximum measurable polarisation intensity extinction ratio to ~40 dB. Implications for polarisation measurements and fibre gyros are outlined.
42 citations
TL;DR: Experimental results are presented that illustrate the excellent reproducibility and thermal stability of fiber polarizers made by coiling highly birefringent bow-tie fibers.
Abstract: Experimental results are presented that illustrate the excellent reproducibility and thermal stability of fiber polarizers made by coiling highly birefringent bow-tie fibers. The effective extinction ratio of the polarizer when used in a fiber-optic gyroscope is shown to be 62 dB.
32 citations
TL;DR: In this paper, the fabrication and operation of the first cleaved-coupled-cavity (C3) semiconductor laser with large cavity length ratios is described. But the internal cleaved facet is precisely positioned by photochemically etching a groove through most of the wafer.
Abstract: The fabrication and operation of the first cleaved‐coupled‐cavity (C3) semiconductor lasers with large cavity length ratios are described. The internal cleaved facet is precisely positioned by photochemically etching a groove through most of the wafer. Single longitudinal mode operation is obtained over a temperature range of 21 °C and over a current range of threshold to greater than four times threshold. Sidemode suppression of 100:1 was measured when the laser was modulated at 350 MHz with an extinction ratio greater than 10:1. These results are experimentally and theoretically compared to approximately equal length C3 lasers.
21 citations
TL;DR: In this paper, the experimental results on two types of electrooptically controllable leaky anisotropic waveguides using nematic liquid crystal (LC) overlayers were described.
Abstract: This paper describes the experimental results on two types of electrooptically controllable leaky anisotropic waveguides using nematic liquid crystal (LC) overlayers. In these constructions the conversion of a guiding structure into a leaky one or a reverse operation is feasible by applying an electric field. They showed a switching of millisecond order with an extinction ratio of 20 dB at 30-V peak-to-peak (p-p) applied.
16 citations
TL;DR: In this article, two distinctly different integrated optical polarisers have been made with multilayer claddings and titanium indiffused lithium niobate waveguides, transmitting both TE and TM polarisations.
Abstract: Two distinctly different integrated optical polarisers have been made with multilayer claddings and titanium indiffused lithium niobate waveguides, transmitting both TE and TM polarisations. The TE device used claddings on the crystal surface obtaining (20.9±0.3) dB/cm extinction ratio. The TM polariser used similar claddings on a vertical wall fabricated by ion-beam milling adjacent to the waveguide, obtaining (17±3) dB extinction ratio.
14 citations
TL;DR: Theoretical performances of integrated polarisers realised by metallic coating of planar waveguides on an oxidized silicon substrate are discussed in this article, giving extinction ratios in excess of 40 dB, with attenuations lower than 1 dB, and interaction lengths of about 2 mm.
Abstract: Theoretical performances of integrated polarisers realised by metallic coating of planar waveguides on oxidised silicon substrate are discussed. Measurements are reported for aluminium and chromium-gold coatings, giving extinction ratios in excess of 40 dB, with attenuations (TE polarisation) lower than 1 dB, and interaction lengths of about 2 mm.
12 citations
Patent•
11 Oct 1984
TL;DR: In this article, a 1/2 wave plate was arranged between a beam splitter and a stop-down lens to reduce the extinction ratio and realize the high S/N reproduction by arranging a 1 2 wave plate between the polarizing beam splatter and stop down lens.
Abstract: PURPOSE:To reduce the extinction ratio and realize the high S/N reproduction by arranging a 1/2 wave plate between the polarizing beam splitter and stop- down lens. CONSTITUTION:A 1/2 wave plate 4 is arranged between a beam splitter 3 and a stop-down lens 5. The optical beam emitted from a semiconductor laser 1 is made into parallel lights by a collimater lens 2, passes through the beam splitter 3, and irradiated after being stopped-down by the lens 5. Its reflecting light is detected by an optical detector 11 through a lens 10. At that time, since the 1/2 wave plate is being arranged, the direct polarized light surface can be coincided with optical anisotropic axis of the lens 5. Therefore, extinction ratio, which is the ratio against light quantity leaked from the analyzer 9 can be reduced and high S/N reproduction can be made.
9 citations
TL;DR: The formulae show that in shot-noise limited systems there is an optimum angle between the polarization planes of the polarizer and analyser and that, once this angle is employed, the signal-to- noise ratio of the system cannot be appreciably improved by improving the quality of the Polarizer used.
TL;DR: The near infrared magneto-optical properties of the yttrium iron garnet single crystal (YIG) grown by the traveling solvent floating zone (TSFZ) method are presented in this article.
Abstract: The near infrared magneto-optical properties of the yttrium iron garnet single crystal (YIG) grown by the traveling solvent floating zone (TSFZ) method are presented in this paper. In fibre-optic communications YIG has been given attention as a magneto-optical and an optical nonreciprocal material. But there is little information about these properties for the available YIG. New data for YIG we developed are presented, including the absorption spectra, the Faraday rotation spectra, the magnetic field dependences of the extinction ratio and the refractive index spectrum, all in the near infrared. Typical results at 1.3 μm wavelength are (1) absorption coeff. α = 0.27/cm ( 2.0 mm thickness, transmissibility 94.7 % for AR-coated), (2) Faraday rotation Θ F = 222°/cm, (3) extinction ratio k = 2×10-4. Regarding the application of YIG as an optical isolator, the temperature dependences of insertion loss (LF) and isolation (LB) were measured and at 1.3 μm wavelength, 20 °C, LF and LB were 1.4 dB and 33 dB, respectively.
TL;DR: In this article, the extinction ratio of the coupler is 41 dB at a wavelength λ = 1.3 μm with a coupling ratio of 48:52, where ρ = 0.
Abstract: Fused polarising fibre couplers have been fabricated using single-polarisation single-mode fibres. When circularly polarised light is fed into the coupler, one of the two orthogonal polarisation modes suffers strong attenuation, and only one polarisation mode couples in the fused biconical taper region. The extinction ratio of the coupler is 41 dB at a wavelength λ = 1.3 μm with a coupling ratio of 48:52.
Patent•
22 Aug 1984
TL;DR: In this paper, the extinction ratio was obtained by detecting an optical output only when a pulse exists, controlling an LD drive circuit so as to make the output constant and controlling the LD current with the optical output at optical pulse output.
Abstract: PURPOSE:To obtain a prescribed extinction ratio and a peak value by detecting an optical output only when a pulse exists, controlling an LD drive circuit so as to make the output constant and controlling the LD current with the optical output at optical pulse output. CONSTITUTION:A light irradiated from a semiconductor laser LD1 is monitored by a photodetector (PD) 2 and its output is amplified by an amplifier 3. The output of the amplifier 3 is inputted to a sample-and-hold IC6. A sample-and- hold circuit 6 uses a signal 7 as a clock pulse and samples and holds the output of the amplifier 3 when the signal pulse exists. The output of the sample-and- hold circuit 6 controls the LD driver 4. As a result, the optical output with stable extinction ratio is obtained.
TL;DR: A novel fiber-optic device acting simultaneously as a polarizer and a directional coupler is fabricated by coating a metal layer onto the fused biconical-taper structure of single-mode fibers.
Abstract: A novel fiber-optic device acting simultaneously as a polarizer and a directional coupler is fabricated by coating a metal layer onto the fused biconical-taper structure of single-mode fibers. This polarizing directional coupler exhibits an extinction ratio of 15 dB together with a 1:1 power-splitting ratio and an excess loss of 2.8 dB.
DOI•
01 Oct 1984TL;DR: In this article, a directional coupler switch with an extinction ratio better than 35 dB has been fabricated using Ti-indiffused waveguides and detailed measurements of voltage, wavelength and temperature response and of the mode intensity profile are given.
Abstract: A directional coupler switch having an extinction ratio better than 35 dB has been fabricated using Ti-indiffused waveguides. Detailed measurements of voltage, wavelength and temperature response and of the mode intensity profile are given. A computer model which allows inaccuracies in fabrication to be included is presented, with results relating extinction ratio to waveguide separation angle and mode confinement.
TL;DR: In this paper, it was shown that significant changes in the lasing field intensity of the device may be achieved using injected optical power comparable to the output of twin-stripe lasers.
Abstract: The optical injection sensitivity of twin-stripe lasers has been characterized in terms of an extinction ratio whose value has been calculated as a function of optical injection power. It is shown that significant changes in the lasing field intensity of the device may be achieved using injected optical power comparable to the output of twin-stripe lasers. The effects described are seen to be relevant to a prediction of optically induced bistability made in an earlier work.
TL;DR: In this article, the extinction ratio of metal-clad optical waveguides with low index dielectric tapered buffer layer has been experimentally studied and it was shown that TE-and TM-modes depend strongly on the tapered angle θ and the length L.
Abstract: Propagation characteristics of metal-clad optical waveguides with low index dielectric tapered buffer layer have been experimentally studied. The extinction ratio of TE- and TM-modes depends strongly on the tapered angle θ and the length L. The extinction ratio of 22 dB for θ = 0.0015 rad and L = 0.35 mm was observed.
Patent•
05 Jul 1984
TL;DR: In this article, the authors proposed a connecting method between a waveguide type optical element and incident and exit optical fibers for retaining plane of polarization by interposing single mode fibers of a specific length between the waveguide and the optical fibers.
Abstract: PURPOSE:To provide a simple connecting method between a waveguide type optical element and incident and exit optical fibers for retaining plane of polarization by interposing single mode fibers of a specific length between the waveguide type optical element and the optical fibers for retaining plane of polarization. CONSTITUTION:Four incident single mode fibers 2 are connected on the end faces of the four incident light waveguides of a waveguide type optical switch 12, and four exit single mode fibers 10 are connected to the end faces of the four exit light waveguides. The respective fibers 2, 10 are linear, and the length Z thereof is maintained at Z<=0.20/DELTAbeta in order to transmit a light wave by using the fibers 2, 10 of which the difference in propagation constant with respect to optional two polarized waves intersecting orthogonally with each other is DELTAbeta radian/meter and maintaining the same at an extinction ratio -20dB. Thus, when the light wave of either mode of TM or TE is made incident to optical fibers 1 for retaining plane of polarization, the mode of either TM or TE is maintained when the light wave arrives at the incident end face of a 4X4 waveguide type optical switch.
23 Jan 1984
TL;DR: In this paper, the effect of an imperfect polarizer was analyzed and it was shown that a phase bias results which is proportional to the polarizer amplitude extinction ratio, which causes an offset in the apparent rotation rate from its true value.
Abstract: Optical polarization requirements were recognized early in the development of fiber-optic gyroscopes. The preferred position of the polarizer in the optical gyro circuit was given by Ulrich. 1 An analysis of the effect of an imperfect polarizer was carried out by Kintner,2 who showed that a phase bias results which is proportional to the polarizer amplitude extinction ratio. This phase bias causes an offset in the apparent rotation rate from its true value. Estimates of the required polarizer quality for specified gyroscope performance have been difficult to state largely due to the lack of a quantitative model. Experimental intensity extinction ratios reported for gyroscope polarizers range from 50 (Ref. 3) to 90 dB.4
Patent•
08 Sep 1984
TL;DR: In this article, an optical output control circuit for a laser diode LD driven by the sum Ip+Ib of pulse currents Lp interrupted by signal pulses and DC bias currents Ib is provided.
Abstract: PURPOSE:To prevent the variation (an extinction ratio of light does not change) of an optical output and the amplitude of a pulse output photoelectric-converted by changing both the DC bias of a laser diode and the amplitude of pulse currents. CONSTITUTION:An optical output control circuit for a laser diode LD driven by the sum Ip+Ib of pulse currents Lp interrupted by signal pulses and DC bias currents Ib is provided with a thermo-unit TU containing a thermistor having approximately the same temperature characteristics as the temperature change characteristics of the threshold currents of the laser diode LD, a means controlling DC bias currents Ib in response to an output from the thermo-unit TU, a photodiode PD monitoring back beams from the laser diode LD, and a means varying said pulse currents Ip in response to the change of the light-receiving currents of the photodiode PD.
Patent•
12 Jan 1984
TL;DR: In this article, a CML (current mode logic) circuit is used in a high speed laser driving circuit, which is constituted by transistors 10 and 12 and a resistor 14.
Abstract: PURPOSE:To obtain a laser driving circuit, which can always secure a constant light output and an extinction ratio in an usable temperature range and does not have fluctuation in output waveforms, by flowing a bias current, which is varied with the variation in threshold value of laser light due to temperature change, to a semiconductor laser, controlling an input signal that is applied to one of transistors, thereby compensating for quantum efficiency variation due to the temperature change. CONSTITUTION:A CML (current mode logic) circuit is used in a high speed laser driving circuit. A thermistor 24 is inserted in a common emitter circuit. The CML is constituted by transistors 10 and 12 and a resistor 14. Said thermistor 24 has replced a part of the emitter resistor of the CML. A capacitor 26 bypasses an AC component. An input signal Sg is applied to the transistor 10, and a reference voltage Vr is applied to the other transistor 12. The resistances of the fixed resistor 14 and the thermistor 24 are suitably selected so as to obtain Sg>Vr. The current value is set so that it is varied with the temperature when a current is switched from the transistor 12 to the transistor 10. The average light output of a laser 20 is detected, and the signal Sg is adjusted so that the output becomes constant.
Patent•
11 Apr 1984
TL;DR: In this paper, a PCM input signal from a gate circuit G is converted into a level, which can be driven, by a driver DRIV, an output from the driver and bias currents from a comparator COM2 are overlapped by an adder ADD, and the semiconductor laser LD is driven by a signal from the adder.
Abstract: PURPOSE:To keep a peak value constant while maintaining a desired extinction ratio by independently controlling bias currents and the level of a pulse signal when the pulse signal is overlapped to DC bias currents and a semiconductor laser is driven by using a drive signal obtained by the overlapped currents. CONSTITUTION:A PCM input signal from a gate circuit G is converted into a level, which can be driven, by a driver DRIV, an output from the driver and bias currents from a comparator COM2 are overlapped by an adder ADD, and the semiconductor laser LD is driven by a signal from the adder. The backward output of laser beams from a laser LD is received by using an avalanche photodiode APD, an output from the photodiode is amplified by a wide zone amplifier AMP, and added to a peak detector DET2, and the peak value is clamped first, and DCs are cut by a DET3, and pulse height is detected. The difference is compared with reference voltage by the comparator COM2, pulse height is compared by a COM1, and bias currents and the pulse signal are controlled separately.
Patent•
04 Aug 1984
TL;DR: In this paper, the extinction ratio at a region with less bias current was obtained by performing optical output control by bias current/pulse current in response to a low/high temperature region of a laser diode to stabilize the optical output.
Abstract: PURPOSE:To obtain a large extinction ratio at a region with less bias current by performing optical output control by bias current/pulse current in response to a low/high temperature region of a laser diode to stabilize the optical output control. CONSTITUTION:In a high speed switching circuit SW, a transistor (TR)1 is turned off when a pulse of an input signal Sin is positive and a TR2 is turned on and when the pulse is negative, the TR1 is turned on and the TR2 is turned off, a current applied from a constant current circuit CCP flows to the TR1 of TR2 and a pulse current IP is supplied to a laser diode LD. A constant current circuit CBC supplies a bias current IB proportional to a voltage applied from an amplifier APC to the LD. A limiter LIM controls the output of the APC by a setting voltage of a resistor Rv2. Further, the CCP supplies a current IP proportional to the supply voltage from the LIM to the SW. Further, the optical output control is performed by the change in the IB at a temperature being T0 or over and by the change in the IP at the T0 or below.
01 Jan 1984
TL;DR: In this article, two types of electrooptically controllable leaky anisotropic waveguides using nematic liquid crystal (LC) overlayers were described. And they showed a switching of milli-second order with an extinction ratio of 20 dB at 30-V peak-to-peak @-p.
Abstract: This paper describes the experimental results on two types of electrooptically controllable leaky anisotropic waveguides using nematic liquid crystal (LC) overlayers. In these constructions the con- version of a guiding structure into a leaky one or a reverse operation is feasible by applying an electric field. They showed a switching of milli- second order with an extinction ratio of 20 dB at 30-V peak-to-peak @-p) applied.