Showing papers on "Extinction ratio published in 1988"
TL;DR: In this paper, a four-channel optical waveguide multi/demultiplexer for 5 GHz spaced optical FDM transmission is developed, and the extinction ratio dependence on the power transfer ratio of the directional couplers, transmission loss of the waveguide, and birefringence of waveguide is investigated.
Abstract: A four-channel optical waveguide multi/demultiplexer for 5-GHz spaced optical FDM transmission is developed. The multi/demultiplexing principle is first presented, followed by the extinction ratio dependence on the power transfer ratio of the directional couplers, transmission loss of the waveguide, and birefringence of the waveguide. Experimental results are described for waveguides of high-silica glass fabricated on the silicon substrate by combination of flame hydrolysis and reactive ion etching. Their measured characteristics, such as frequency transmittance, loss, extinction ratio, and dependence of polarization and temperature are reported and evaluated. >
88 citations
TL;DR: In this article, the amplification characteristics of the distributedfeedback (DFB) laser amplifier have been studied and the amplifier can be applied as an optical narrowband filter with an extinction ratio of better than -15 dB for optical inputs separated by 9.8 GHz.
Abstract: The amplification characteristics of the distributed-feedback (DFB) laser amplifier are studied. The amplifier has a narrow, single-frequency gain-bandwidth product and the maximum-gain frequency tunability. With these advantages, the amplifier can be applied as an optical narrowband filter. This filter has optical frequency selectivity with an extinction ratio of better than -15 dB for optical inputs separated by 9.8 GHz having different optical input powers. By using a multielectrode DFB laser amplifier, the wide-range tunability of a gain maximum frequency (33.3 GHz) can be obtained while maintaining a constant gain and a constant gain-bandwidth product. Optical frequency selection with an extinction ratio of better then -20 dB can be obtained for two optical inputs separated by 15.4 GHz and having the same input power. >
69 citations
01 Jan 1988
TL;DR: In this article, the authors predict the transmission characteristics of waveguide transitions and junctions to understand and optimize device performance, which is useful to be able to predict the waveguide transmission characteristics in terms of extinction ratio and crosstalk.
Abstract: Most useful waveguide devices use a series of waveguide transitions or junctions where the cross section of the waveguide structure changes in the direction of propagation. For example, transitions are typically placed on both sides of a phase shift region to form an electrooptical switch. The performance of the switch in terms of extinction ratio and crosstalk depends critically on how well those transitions perform their intended function. To understand and optimize device performance it is therefore useful to be able to predict the transmission characteristics of waveguide transitions and junctions.
35 citations
TL;DR: In this paper, the biconically-tapered-fused (BTF) fiber coupler fabrication approach to polarization preserving fiber couplers is reported. And two practical methods for identifying and aligning the birefringent axes of the fibers forming the coupler are described.
Abstract: The adaptation of the biconically-tapered-fused (BTF) fiber coupler fabrication approach to polarization preserving fiber couplers is reported. Two practical methods for identifying and aligning the birefringent axes of the fibers forming the coupler are described. The fabrication approaches are highly reproducible and the 3-dB couplers fabricated exhibit less than 1.0-dB insertion loss, controllable splitting ratio, and an average polarization extinction ratio of 15 to 20 dB. >
23 citations
TL;DR: Quaternary AlGaInAs quantum-well optical modulators operating at 1.55 mu m are introduced and demonstrated for the first time in this paper, where an electron-to-heavy-hole exciton absorption peak shift of over 600 AA is observed for a bias voltage of 6 V.
Abstract: Quaternary AlGaInAs quantum-well optical modulators operating at 1.55 mu m are introduced and demonstrated for the first time. An electron-to-heavy-hole exciton absorption peak shift of over 600 AA is observed for a bias voltage of 6 V. An extinction ratio of 19 dB and high-speed operation over 4 GHz is obtained for this optical modulator. >
23 citations
TL;DR: In this paper, an all-fibre polariser was demonstrated utilizing the birefringent properties of a nematic liquid crystal having refractive indices compatible to that of fused silica, achieving an extinction ratio in excess of −45dB and a loss of 0.2dB over a temperature range between 10 and 50°C.
Abstract: An all-fibre polariser is demonstrated utilising the birefringent properties of a nematic liquid crystal having refractive indices compatible to that of fused silica. The polariser exhibits an extinction ratio in excess of −45dB and a loss of 0.2dB over a temperature range between 10 and 50°C. Design considerations to achieve a desired extinction ratio are also discussed.
21 citations
Patent•
27 Aug 1988
TL;DR: In this paper, a laser diode image setter with multiple resolution operating modes is proposed to stabilize the optical output power from the semiconductor laser-diode during the scan trace interval across a photosensitive material so as to maintain a high extinction ratio for the laser, even when its driving current is changed to a different level.
Abstract: A laser diode image setter having multiple resolution operating modes, includes means for stabilizing the optical output power from the semiconductor laser diode during the scan trace interval across a photosensitive material so as to maintain a high extinction ratio for the laser diode even when its driving current is changed to a different level in order to operate the image setter at a different resolution mode.
20 citations
TL;DR: In this paper, a 4.8 cm W-tunnelling fiber polariser was used to achieve a 39 dB polarisation extinction ratio over a useful bandwidth of 4% centred at 633 nm.
Abstract: Measurements of a 4.8 cm W-tunnelling fibre polariser show a 39 dB polarisation extinction ratio over a useful bandwidth of 4% centred at 633 nm.
20 citations
TL;DR: In this paper, a nonsymmetric Mach-Zehnder interferometer was proposed, which has both low switching voltage and efficient coupling to microwave-frequency drive circuits and achieved better than 20dB extinction ratio at lambda = 1.3 mu m.
Abstract: Optical communications systems require fast optical modulators which are compatible with existing microwave-frequency drive circuits and which have low voltage requirements. The authors have designed and demonstrated a novel type of integrated optical modulator: a nonsymmetric Mach-Zehnder interferometer, which has both low switching voltage and efficient coupling to microwave-frequency drive circuits. In 2-cm-long devices, made in z-cut LiNbO/sub 3/, switching voltages of 3.2 V and better than 20-dB extinction ratio were measured at lambda =1.3 mu m. Device performance in the nonsymmetric devices was independent of the asymmetry, which indicates that devices of this kind are tolerant of fabrication variations. >
14 citations
TL;DR: A system model for analyzing the effects of dispersion when multilongitudinal-mode laser diodes are used and a statistical approach to route design is demonstrated.
Abstract: A system model for analyzing the effects of dispersion when multilongitudinal-mode laser diodes are used is presented. The analysis considers in a general manner the digital symbol statistics, the system pulse shaping, the laser diode spectrum, the laser diode extinction ratio, and mode partition noise. For mode partition noise, separate consideration is given to the statistics of the longitudinal-mode powers within a baud period and to the statistics between different baud periods. It is demonstrated that failure to separate the mode partition statistics in this manner can lead to underestimation of the dispersion penalty. By incorporating statistical models for the important system parameters, a statistical approach to route design is demonstrated. >
14 citations
TL;DR: An eigenvalue equation is derived for stratified metallic optical slab waveguides with any number of layers and the equation is solved using the numerical zoom analysis (NZA) method, which may be useful for optimizing the design parameters.
Abstract: An eigenvalue equation is derived for stratified metallic optical slab waveguides with any number of layers. The equation is solved using the numerical zoom analysis (NZA) method. The analysis is applied to various metallic optical slabs and the propagation characteristics of the guided waves are determined, which may be useful for optimizing the design parameters. It is found possible, with proper optimization, to design a polarizer having hundreds of decibels of extinction ratio at the cost of a fraction of a decibel of insertion loss. Examples of optimizations with respect to wavelength, relative refractive indices, core/clad geometries, etc. are demonstrated for slabs with single or double metal layers. Guidelines for determining the metal film thickness have been formulated and tabulated for many useful metals.
Patent•
11 Jan 1988
TL;DR: In this paper, the authors proposed a method to divide optical signals having narrow wavelength intervals with a small extinction ratio by installing a means which gives an optical loss to at least one of two optical waveguides.
Abstract: PURPOSE:To divide optical signals having narrow wavelength intervals with a small extinction ratio, by installing a means which gives an optical loss to at least one of two optical waveguides. CONSTITUTION:When multiplexed optical signals lambda1 and lambda2, whose wavelengths are about 1.55mum and wavelength intervals are about 0.1nm, are inputted, the optical signal lambda1 and lambda2 are branched at a ratio of about 1:1 by means of an optical coupler 3 and propagated to two optical waveguides 2a and 2b having different optical paths. Since the optical waveguides 2a and 2b have different optical paths, radii of curvature, etc., their propagation losses are different from each other and, as the waveguide 2b has a longer optical path and smaller radius of curvature as compared with the other waveguide 2a, the propagation loss of the wavelength 2b is larger than that of the other waveguide 2a by about 1dB. Therefore, the optical signals lambda1 and lambda2 propagated through the optical waveguide 2b become smaller in power than those propagated through the other waveguide 2 by about 1dB. Accordingly, a voltage of about 10V is impressed across electrodes 4 and sothat the specific refractive index of the optical waveguide 2a' can be made smaller and the radiation mode can be made larger. Thus the powers of the optical signals lambda1 and lambda2 propagated through the optical waveguides 2a are made smaller by about 0.5dB so as to make the difference in propagation loss between the two optical waveguides 2a and 2b smaller by about 0.5dB.
TL;DR: In this paper, the application of a semiconductor-laser amplifier with reduced facet reflectivity as all-optical switch is described, where the two optical signals are polarized perpendicularly to each other.
Abstract: The application of a semiconductor-laser amplifier with reduced facet reflectivity as all-optical switch is described. An optical data signal is switched on and off with an extinction ratio of 10 dB when an optical control signal is turned on and off. The two optical signals are polarized perpendicularly to each other. The device was operated up to 100 MHz.
TL;DR: In this article, the maximum number of connectable laser diode optical switches (LDSWs) was studied through the baseband signal-to-noise ratio calculation, and 60 stages of LDSWs were connected with a 6-nm optical bandpass filter inserted after the last stage at an input signal level of −30 dB m and an internal gain of 16 dB.
Abstract: The maximum number of connectable laser diode optical switches (LDSWs) was studied through the baseband signal-to-noise ratio calculation. For an NRZ 100 Mbits−1 PCM-IM signal, 60 stages of LDSWs can be connected with a 6-nm optical bandpass filter inserted after the last stage at an input signal level of −30 dB m and an internal gain of 16 dB. A PCM-IM signal of 10 Gbits−1 can be transmitted through 130 stages of LDSWs at an internal gain of 8 dB and an input signal level of −20 dB m.
Patent•
09 Feb 1988
TL;DR: In this paper, an air layer between a nonreflective coat surface of a triangular block and non-reflective surface surfaces of input and output side beam splitters was formed to reduce an error of a frequency difference of multiplexing and demultiplexing light beams.
Abstract: PURPOSE:To reduce an error of a frequency difference of multiplexing and demultiplexing light beams, to improve an extinction ratio of light, and to easily execute an adjustment to a polarized wave direction, by forming an air layer between a non-reflective coat surface of a triangular block and non-reflective coat surfaces of input and output side beam splitters. CONSTITUTION:Input side and output side beam splitters 3, 6 are fixed adjacently, and on the upper faces of each beam splitter 3, 6, non-reflective coat surfaces 3a, 6a are formed. To each non-reflective coat surface, piezoelectric elements 12, 12 are fixed, and to both its side parts, electrodes 12a, 12a are attached and connected to each other through a driving circuit 11. Also, to the upper part of each piezoelectric element 12, a triangular block 20 is fixed, and an incident luminous flux from the input side beam splitter 3 is refracted and made incident on the output side beam splitter 6 as a reflected luminous flux. Subsequently, on both slant faces of the triangular block 20, total reflecting mirrors 21, 22 are formed, a non-reflective coat surface 23 is formed on the surface of the piezoelectric element 12, 12 sides, and an air layer 24 is formed between the non-reflective coat surface 3a and 6a. In this way, an error of a frequency difference of multiplexing and demultiplexing light beams is reduced, a saving adjustment of a polarized wave direction of light is executed easily, and an extinction ratio is not deteriorated.
TL;DR: In this article, a polarization-independent Mach-Zehnder interferometric light modulator consisting of z-propagation Ti-indiffused waveguides is fabricated on an x-cut LiNbO3 substrate in which electrically induced phase shifts are nearly identical for TE and TM modes.
Abstract: A polarization-independent Mach-Zehnder interferometric light modulator consisting of z-propagation Ti-indiffused waveguides is fabricated on an x-cut LiNbO3 substrate in which electrically induced phase shifts are nearly identical for TE and TM modes. The optimum Ti-film thickness for making the modulator is determined by measurements on the electrooptic property of the waveguides. Using the modulator we have achieved an extinction ratio of ~17 dB with a 14.5 V drive voltage for both modes and low sensitivity to optical damage at a wavelength of 633 nm.
TL;DR: It is found that the twist, large or small, introduced unintentionally in fused couplers may deteriorate the extinction ratio of polarization splitting when devices are used as polarization beam splitters, and that the modulation period of the spectral response of fused coupler can be tuned by controlling the twist rate.
Abstract: The effect of twist on fused couplers is discussed theoretically. We find that the twist, large or small, introduced unintentionally in fused couplers may deteriorate the extinction ratio of polarization splitting when devices are used as polarization beam splitters, and that the modulation period of the spectral response of fused couplers can be tuned by controlling the twist rate when they are used as wavelength filters.
01 Jun 1988
TL;DR: In this article, an interactive computer program is described that enables the user to calculate the phase function, extinction, scattering and absorption efficiencies, the mass extinction coefficient and backscatter to extinction ratio for most particulate clouds.
Abstract: : An interactive computer program is described that enables the user to calculate the phase function, extinction, scattering and absorption efficiencies, the mass extinction coefficient and backscatter to extinction ratio for most particulate clouds. These clouds may be composed of either mono- or polydispersed particles of the following geometries: sphere, coated sphere, infinite cylinder, coated infinite cylinder, finite cylinder or various irregular shapes. The non-spherical regular shapes may be either oriented or have random orientation. Australia.
Patent•
20 Dec 1988
TL;DR: In this paper, the extinction ration is detected by receiving a part of an outputted intensity modulation light beam by a light receiver, and a voltage applied between electrodes 17, 18 is controlled so that the extinction ratio becomes maximum.
Abstract: PURPOSE:To prevent the deterioration of an extinction ratio caused by a temperature variation, a secular change, etc. by detecting the extinction ratio by receiving a part of an outputted intensity modulation light beam by a light receiver, and controlling a voltage applied between electrodes so that the extinction ratio becomes maximum. CONSTITUTION:An extinction ration is detected by receiving a part of an outputted intensity modulation light beam by a light receiver 21, and a voltage applied between electrodes 17, 18 is controlled so that the extinction ratio becomes maximum. That is, a light receiving signal of the receiver 21 is amplified by an amplifier 22, and inputted to a waveform observing device 23 such as an oscilloscope, etc. A control circuit 24 for controlling a driving circuit 25 so that an extraction ratio of a detected output light becomes maximum is provided. The driving circuit 25 sets the voltage applied to the electrodes 17, 18 in accordance with an inputted digital modulating signal, and also, adjusts an operation point in an operation characteristic curve in accordance with a control signal from the control circuit 24. That is, the reference potential is adjusted to a voltage for applying the maximum or the minimum output light intensity. In such a way, the deterioration of the extinction ratio caused by a temperature variation, etc. is prevented and the operation of an optical modulator can be stabilized.
TL;DR: In this article, a planar optical polarisation splitter for simultaneous extraction of both TE and TM modes is proposed and demonstrated, which consists of a periodic waveguide section joined by straight tapered transitions to smooth regions.
Abstract: A novel planar optical polarisation splitter for simultaneous extraction of both TE and TM modes is proposed and demonstrated. Our device, designed according to the principle of the polarisation-dependent direction of energy flow near Bragg incidence, consists of a periodic waveguide section joined by straight tapered transitions to smooth regions. Experimentally, a minimum extinction ratio of 17dB was achieved.
DOI•
01 Feb 1988
TL;DR: In this article, an alternative theoretical treatment for electroabsorption at the fundamental absorption edge of semiconductors is compared with experimental results in high purity MOCVD grown GaAs, and acceptable agreement between theory and experiment is demonstrated for wide ranges of wavelengths (0.85?1.0?m), and applied fields (up to the breakdown field).
Abstract: An alternative theoretical treatment for electro-absorption at the fundamental absorption edge of semiconductors is compared with experimental results in high purity MOCVD grown GaAs. For the first time, acceptable agreement between theory and experiment is demonstrated for wide ranges of wavelengths (0.85?1.0 ?m), and applied fields (up to the breakdown field). It is shown that these results enable optimised electroabsorption modulators to be designed for low insertion loss, high extinction ratio, high cut off frequency, and wide optical bandwidth. The feasibility of waveguide device with performance parameters higher than any reported to date (with or without the use of quantum wells) is predicted, and experimental devices are reported which approach these predictions at low frequencies of operation.
TL;DR: In this article, the insertion loss and extinction ratio were 0.6 and 22 dB respectively, at a wavelength of 1.3 mu m. The device size was only 4 mm in diameter and 25 mm in length.
Abstract: At low-loss fibre optic polariser is fabricated by embedding a thin polarisation-splitting chip in a single-mode fibre. The insertion loss and extinction ratio were 0.6 and 22 dB respectively, at a wavelength of 1.3 mu m. The device size was only 4 mm in diameter and 25 mm in length.
25 Jan 1988
TL;DR: In this paper, the extinction ratio of linear stress-induced birefringent fibers is defined as the ratio of power leakage into the unexcited mode to that of the total input power, and the fundamental limits of cross-polarization in polarization-maintaining (PM) fibers have been described as intrinsic1-3 or internal, extrinsic, or external and measurement related.
Abstract: An important characteristic of linear stress-induced birefringent fibers is the extinction ratio of cross-polarization, which is defined as the ratio of power leakage into the unexcited mode to that of the total input power. The fundamental limits of cross-polarization in polarization-maintaining (PM) fibers have been described as intrinsic1-3 or internal, extrinsic,4 or external and measurement related.5 Extinction ratio measurements are reported on two lengths (1 and 100 m) of an AT&T rectangular PM fiber6 and compared to published cross-polarization coupling limitations.
TL;DR: In this paper, a TE-pass polariser with MgO buffer layer and various metal claddings (Al, Au and Ti) was used for lambda =780 nm and achieved an extinction ratio up to 55 dB and TM attenuation of 250 dB/cm using Al cladding.
Abstract: TE-pass polarisers with MgO buffer layer and various metal claddings (Al, Au and Ti) have been realised. For lambda =780 nm the samples showed an extinction ratio up to 55 dB and a TM attenuation of 250 dB/cm using Al cladding.
TL;DR: In this paper, the scalar wave equation is used to investigate the resonant effect of a slight deviation from the resonance condition virtually stops the exchange of energy between two parallel fibers.
Abstract: A slight deviation from the resonant condition virtually stops the exchange of energy between two parallel fibers. When one fiber is birefringent, and the other isotropic and lossy, the energy of only one polarization mode swaps back and forth between two fibers and is eventually absorbed. The scalar wave equation is used to investigate the resonant effect. It is found that energy conservation is an intrinsic property of the solution of the scalar wave equation for any trial function, and that standard coupled mode equations obtained from Maxwell's equations can be derived from the scalar wave equation in an exact way. The resonant effect discussed can provide very high extinction ratio at extremely low penalty of additional loss. For example, an extinction ratio of 1.2*10/sup 4/ dB with a penalty of 0.2 dB can be expected after 1-km transmission for waveguide parameters common in fiber optics. >
TL;DR: Analytical results are presented that describe the characteristics of fused single-mode tapered couplers and the influence of coupler geometry on polarization splitting and spectral selectivity is investigated.
Abstract: Analytical results are presented that describe the characteristics of fused single-mode tapered couplers. The influence of coupler geometry on polarization splitting and spectral selectivity is investigated. A selective fused coupler has been made that exhibits a channel separation of Δλ = 0.6 nm, an insertion loss of 1 dB, and an extinction ratio of 20 dB. Polarization selectivity of 20 dB has also been achieved.
TL;DR: In this paper, the realisation of a 2 × 2 switch using a Mach-Zehnder interferometer with tunable coupler sections is described, which is based on a GaAs-AlGaAs double heterostructure with SnO2-doped In2O3 electrodes.
Abstract: The letter reports the realisation of a 2 × 2 switch using a Mach-Zehnder interferometer with tunable coupler sections. The structure is based on a GaAs-AlGaAs double heterostructure with SnO2-doped In2O3 electrodes. At a wavelength of 1.15 μm, this device is characterised by a low switching voltage of 7.5 V and a low loss of 4 dB/cm. A high extinction ratio of 20 dB can be achieved.
TL;DR: In this paper, an all polarisation maintaining (PM) fiber heterodyne 1.4 Gbit/s DPSK system experiment is demonstrated and good and stable polarisation extinction ratio (>20 dB) is achieved while using low loss keyed connectors between the various optical components.
Abstract: An all polarisation maintaining (PM) fibre heterodyne 1.4 Gbit/s DPSK system experiment is demonstrated. Good and stable polarisation extinction ratio (>20 dB) is achieved while using low loss keyed connectors between the various optical components. A bit error rate (BER) lower than 10/sup -9/ is measured for both short (10 m) and long (2.6 km) AT&T PM fibres. >
10 Mar 1988
TL;DR: In this article, a Ti:LiNb03 waveguide high speed Mach-Zehnder interferometric modulator operating at 1.3 um wavelength was designed and fabricated.
Abstract: We have designed and fabricated a Ti:LiNb03 waveguide high speed Mach-Zehnder interferometric modulator operating at 1.3 um wavelength. Design considerations for optical waveguide and traveling-wave coplanar-waveguide electrode have been listed. The modulator was optimized with respect to optical insertion loss, switching voltage or drive power, and modulation bandwidth. The fiber-pigtailed device had a 5 dB fiber-to-fiber loss and an intrinsic modulation bandwidth of 18 GHz. The voltage required to switch the device from the on- to off-state was measured to be 9.5 V, with an on/off extinction ratio of 33 dB.© (1988) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
Patent•
27 Apr 1988
TL;DR: In this article, the extinction ratio of a laser diode is maintained by holding the bias current of the diode constant and controlling a pulse current that the peak value of an optical output power is constant.
Abstract: PURPOSE:To maintain the extinction ratio of a laser diode constant by holding the bias current of the diode constant and so controlling a pulse current that the peak value of an optical output power is constant. CONSTITUTION:An initialized bias current always flow in a laser diode LD5 by a constant-current source 2. The current of a voltage control type current source 12 is switched by a switch 3 to a resistor 4 or the LD5 according to 'H' or 'L' of an input digital signal 13, and a current of IBIAS or IBIAS+Ipulse flows to the LD5. The output light of the LD5 is partly photodetected by a photodiode 8 as a monitoring light 6, its mean power is converted to a voltage level, and fed back to an LD pulse current through a differential amplifier 10 and a constant-current source 12 so that the average value of the optical output power of the LD5 becomes constant, and the LD pulse current is so controlled that the peak value of the optical output power becomes constant.