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Lightwave Technology, Journal of

Issue 12 • Date December 1987

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Displaying Results 1 - 25 of 27
  • [Front cover and table of contents]

    Page(s): 0
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    Freely Available from IEEE
  • [Back cover]

    Page(s): c4
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    Freely Available from IEEE
  • Bandwidth of forward and backward coupling directional couplers

    Page(s): 1773 - 1777
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    This paper deals with the filter properties of directional couplers. Formulas are derived for the bandwidth in wavelength units of couplers consisting of two waveguides that exchange their power either in the direction of the incident wave (forward couplers) or in the opposite direction (backward couplers). Backward couplers require the presence of a diffraction grating on one or both waveguides but they can achieve very much smaller bandwidth than forward couplers and hence are useful for constructing narrow-band optical wavelength filters. View full abstract»

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  • Optical waveguide dispersion characteristics from the scalar wave equation

    Page(s): 1748 - 1754
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    The electric and magnetic fields of an optical waveguide are well represented as derivatives of a linearly polarized vector potential. This vector potential obeys a scalar wave equation. Through the use of a variational principle one may obtain good approximations to the dispersion relation, however, without resolution of the birefringence. A simple perturbational approach yields the birefringence. Universal plots may be obtained in this way for TE and TM modes for rectangular channel waveguides with small index discontinuities. View full abstract»

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  • Single-mode optical fiber connection to high-silica waveguide with fiber guiding-groove

    Page(s): 1716 - 1720
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    Single-mode optical fiber connection to high-silica ridged waveguide formed on a silicon substrate is experimentally described. Fiber alignment and fixing processes are easily accomplished using a guiding groove fabricated at the waveguide end. An average connection loss of 0.4 dB was achieved. Optimum groove configuration, temperature stability of fiber connection, and polarization maintaining characteristics are discussed with experimental results. View full abstract»

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  • Analysis of a phase mismatched three waveguide coupler with an optical amplifier

    Page(s): 1763 - 1767
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    A novel optical amplifier is proposed and analyzed. This device consists of three parallel waveguides and each has a slightly different propagation constant, that is, each waveguide is slightly phase mismatched and couplings among these waveguides are weak. Two adjacent waveguides are passive and the third one is active and all end facets of waveguides are antireflection coated, so that optical feedback can be eliminated and the active waveguide is a traveling wave type amplifier. Because of a phase mismatched configuration, this device can be used to tap optical signals without much power reduction in optical transmission lines. Signals coming into the device are weakly coupled to the active waveguide via the passive waveguide in between and they are amplified through the active waveguide. Characteristics of this device are studied and parameters which are required to design the device are also given as an example. View full abstract»

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  • Long distance fiber-optic transmission of C-band microwave signals to and from a satellite antenna

    Page(s): 1733 - 1741
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    We demonstrate here the use of high-speed semiconductor lasers and detectors with low loss optical fiber for the transmission of the 500-MHz C-band microwave signal spectrum to and from a satellite antenna. The optical system has low attenuation and large band, width, so the microwave signals can be transmitted directly at the microwave frequency (4 or 6 GHz) over 20 km of fiber without regeneration or qualization. The optical system introduces ≈ 1 dB or less of degradation for both low spectral density QPSK signals and high spectral density FM video signals present in typical satellite transmission systems. For the video signals, the signal to noise after AM conversion was reduced from 56 to 55 dB. The microwave drive level to the laser must be significantly larger (typically > -10 dBm) than the intensity noise of the laser, yet small enough (typically < 10 dBm) to reduce the intermodulation distortion signals to an acceptable level. The laser bias current must be several times threshold so that the resonance frequency is beyond the frequency band of interest (4-6 GHz in this case). A flat modulation response is then obtained, and the intensity noise and intermodulation levels are low. View full abstract»

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  • Characterization of the preform stretching process

    Page(s): 1755 - 1762
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    A method of directly measuring the neck diameter profile of a glass boule while it is stretched on a lathe is described. Disturbances to the neck profile Can be detected and controlled. View full abstract»

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  • Protocols for very high-speed optical fiber local area networks using a passive star topology

    Page(s): 1782 - 1794
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    This paper deals with the problem of interconnection of many high-speed bursty traffic users via an optical passive star coupler. Each user can tune its laser over a range of wavelengths, thus resulting in a wavelength division multiplexed communication. The total number of wavelengths over which user tunability exists could be much smaller than the number of users. Therefore, some form of random access sharing and packet switching may be necessary. We propose several protocols that require each user to have a tunable receiver. The information on "where" and "when" to tune the laser is confined to a control (setup) channel that users tune to when in idle mode. An interconnection between two users lasting for the length of a data packet is set up on the control channel by the transmitting user who informs the receiving user where to tune in order to receive the data packet. No centralized control or coordination is required among the users. After analyzing each protocol, we present the throughput/ delay versus the offered traffic and the delay versus throughput in a sequence of plots. We show that in typical applications an average throughput of up to 0.95 can be achieved at a reasonable average delay using one of these protocols. In our benchmark examples we present an optical local area network (LAN) with a total throughput of 100- Gbit/s in which every user has access to a 1-Gbit/s data rate and the network can support over 1000 users. The protocols can be used in a) large LAN's that do not require a large capacity, b) small LAN's (1 kin) that require a large capacity and c) large LAN's (tens of kilometers) that require a rather large capacity. View full abstract»

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  • All-optical fiber-based remote sensing system for near infrared absorption of low-level CH4gas

    Page(s): 1706 - 1711
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    An all-optical remote sensing system utilizing 5-20-km-long, low-loss silica optical fiber links has been developed for the real-time detection of combustible, explosive, and toxic gases in the near infrared region. With this fiber-optic system in conjunction with InGaAsP and InGaAs light emitting diodes (LED's) and a remotely located, compact absorption cell, we have realized a detection sensitivity of less than 25 percent of the lower explosion limit (LEL) of CH4density in air, which is required for any practical CH4gas sensor. This detection sensitivity was confirmed up to a 20-km-long silica optical fiber link with the detection time of 3 s in the CH42nu_{3}band at 1.66 μm and up to nearly 12 km with the detection time of 30 s in the ν2+2nu_{3}band at 1.33 μm. Potential improvement of the sensitivity and detection coverage of the system, as well as its further extensive applications using high power near-infrared LED's or laser diodes (LD's) are also discussed. View full abstract»

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  • Light conversion in nonlinear monomode optical fibers

    Page(s): 1652 - 1659
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    A complementary analysis of the four-wave mixing phenomenon in monomode optical fibers is undertaken. Its central aspect is the interdependence between the amplitudes and the relative phase of the four waves. An expression for the spontaneous emission in terms of the pump power is derived. Investigating the pump depletion it is shown that for short fibers a certain degree of total phase mismatch can be advantageous to the amplification of weak Stokes and anti-Stokes signals. Also the optimal fiber length depends on the initial relative phase. View full abstract»

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  • The solutions of nonaxisymmetric fields in SELFOC fibers with longitudinal imperfections

    Page(s): 1690 - 1694
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    The solutions of nonaxisymmetric fields in SELFOC fibers with longitudinal imperfections are investigated. The refractive index is assumed to be of the formK = varepsilon/varepsilon_{0} = K_{0} - K_{2}(z) r^{2}(K_{2}(z)is a gradually varying function ofz). The analytic solution is obtained. When K2is a constant, the solution is reduced to that of perfect SEL-FOC fibers, which is well known. Further the relations of modes conversion in imperfect fibers are obtained. View full abstract»

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  • Wavelength-division-multiplexing optical switch using acoustooptic deflector

    Page(s): 1742 - 1747
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    A new wavelength-division-multiplexing (WDM) optical switch using an acoustooptic deflector (AOD) is presented. This switch requires minimal hardware and is highly applicable in high-speed signal switching. Theoretical calculations based on the Gaussian beam approximation show that up to a 20 × 20 switch is possible using present technology. As a preliminary study, a 3 × 3 WDM switch is constructed. Crosstalk of this switch is found to be less than -20 dB, and a 500 Mbit/s return to zero (RZ) signal is successfully switched with a 4-μs switch access time. A large capacity switching network using this WDM optical switch is proposed. View full abstract»

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  • Pulse characteristics of Q-switched fiber lasers

    Page(s): 1645 - 1651
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    A theoretical investigation of the anticipated properties of optically end-pumpedQ-switched fiber lasers is reported. This analysis stresses the effect of the transverse structure of the interacting pump and signal (guided) waves, in particular of the fiberVnumber, on the device performance. In Nd : YAG single crystal fibers thresholds as low as a fraction of a milliwatt may be achieved; pulses with peak powers of hundreds of watts and subnanosecond widths may be generated under laser diode pumping conditions. View full abstract»

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  • Dispersion statistics in concatenated single-mode fibers

    Page(s): 1768 - 1772
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    Dispersion measurement data from two sets of fiber cable lengths were employed to determine the histograms of slope and wavelength of zero chromatic-dispersion in concatenated single-mode fibers. We use a Monte-Carlo technique under two concatenating scenarios, depending on whether those fibers being concatenated are or are not manufactured by the same process. Results show that the variances of slope and wavelength of zero dispersion are inversely proportional to the numberNof fiber cable lengths being concatenated. The average and standard deviation of zero-chromatic dispersion wavelength changes less than 0.005 percent or 1 percent, respectively, when the actual dispersion slopes of individual fiber lengths being concatenated are replaced by random quantities distributed with uniformity within 0.08-0.1 ps/km . nm2. View full abstract»

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  • Wavelength dependent properties of He+implanted optical waveguides in LiNbO3

    Page(s): 1660 - 1662
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    The effects of wavelength on the attenuation and propagation constant of TE and TM modes in He+ implanted optical waveguides in LiNbO3are presented. It is shown that the TM mode properties are determined by the ion damage profile, while the TE mode properties are considerably influenced by lithium loss which occurs during implantation. View full abstract»

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  • Intensity effects on the stimulated four photon spectra generated by picosecond pulses in optical fibers

    Page(s): 1712 - 1715
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    The intensity dependence of stimulated four photon mixing (SFPM) spectra generated in 15 m of a 4-mode optical fiber by 25- ps pulses has been investigated. Despite the shortness of pulses, the SFPM conversion was highly efficient due to the intrinsic phase matching condition. In addition to usual features of SFPM spectra generated by nanosecond pump pulses, picosecond SFPM spectra were broadened by self phase modulation (SPM) and cross phase modulation (XPM). At the highest pump powers, intensity saturated frequency continua, arising from the combined effects of SFPM, stimulated Raman scattering (SRS), SPM, and XPM were generated all over the visible spectrum. View full abstract»

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  • Interferometric determination of dispersion variations in single-mode fibers

    Page(s): 1701 - 1705
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    Interferometry is used to study the variation of the zero dispersion wavelength (λ0) and the absolute group index (Ng) along the lengths of depressed cladding single-mode fibers. All of the results are for 34-cm samples of AT&T fibers drawn on production facilities. For two 7.5-km fibers sampled approximately every 1 km,bar{lambda_{0}} = 1299.6 pm 2.7and 1300.5 ± 2.9 nm. For five additional 0.8-km fibers, the average of the end-to-end differences of λ0is 2.0 nm. These results indicate the feasibility of inferring λ0for long lengths of these fibers from measurements made on a 34-cm length. At 1.30 μm,bar{N_{g}}and σ are 1.4659 and 0.0003, respectively (60 fibers from 28 preforms). The corresponding values at 1.55 μm are 1.4666 and 0.0003 (46 fibers from 19 preforms). These results place a lower limit of 0.02 percent on the accuracy of pulse delay measurements of unstressed lengths of AT&T production fibers. View full abstract»

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  • Broad passband multi/demultiplexer for multimode fibers using a diffraction grating and retroreflectors

    Page(s): 1695 - 1700
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    A broad passband multi/demultiplexer for multimode fibers employing a diffraction grating and retroreflectors is presented. As shown by calculation and experimental results, a passband width proportional to the difference between the retroreflector length and the input fiber core diameter is attainable. Using a standard (50/125 mum) graded index fiber as the transmission fiber, 1-dB passband widths of 100 nm for the multiplexing channel and 94 nm for the demultiplexing channel with a channel spacing of 125 nm are achieved in a two-channel multi/demultiplexer. The minimum insertion losses for each channel are 2.3 and 2.7 dB, respectively. View full abstract»

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  • An analysis of a fiber-optic magnetometer with magnetic feedback

    Page(s): 1680 - 1685
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    The magnetic feedback nulling technique in a fiber-optic magnetometer is analyzed both theoretically and experimentally. Results indicate that high nulling efficiency requires large closed loop gain, and large signal-to-noise ratio requires system bandwidth no larger than the signal bandwidth. Large linear dynamic range, freedom from magnetic hysteresis, and long term stability are achievable. View full abstract»

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  • High finesse ring resonators made by silver ion exchange in glass

    Page(s): 1686 - 1689
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    We report the fabrication of single tap ring resonators made by thermal silver ion-exchange in various types of glass substrates. The highest finesse achieved was 55 with an efficiency of 32 percent. We systematically measured losses arising from different sources such as intrinsic absorption in the glass and scattering from side wall roughness arising from the mask fabrication technique. All data was measured atlambda = 0.6328 mum. View full abstract»

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  • Splice loss measurement using local launch and detect

    Page(s): 1663 - 1666
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    This paper reports a new method for measuring absolute splice loss using a local launch and detect technique. The theory of the procedure and the calibration routine are described. Results with single-mode fiber splices are presented and compared with the cutback measurements. View full abstract»

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  • Milled-groove method for fiber-to-waveguide couplers

    Page(s): 1721 - 1726
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    We report a simple milled-groove process integrated with a two-step ion-diffused waveguide fabrication for efficient coupling between single-mode fibers and integrated optical waveguides andY- branches. We demonstrate such a coupling technique using a) a multimode transition to single-mode waveguide coupler, and b) an integrated optical 3-dB branching waveguide coupler from a single-mode fiber to silver/sodium ion-enchanged waveguide components. The coupling loss was about 1-2 dB over a propagation length of 2 cm at an operating wavelength of 633 nm. View full abstract»

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  • Suppression of interface degradation in InGaAsP inP buried heterostructure lasers

    Page(s): 1778 - 1781
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    In InGaAsP/InP buried heterostructure (BH) lasers, the degradation of BH interface between first- and second-growth step layers can be suppressed by employing the melt back process just before the second-step layer growth. It is confirmed this burying process give more reliable BH lasers than the conventional burying process. From the viewpoint of BH interface degradation, lasers lasing at 1.5 μm, where the melt back process naturally occurs during BH formation, are found to be more reliable than those lasing at 1.3 μm. View full abstract»

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  • Fiber-optic subscriber loop systems for integrated services--The strategy for introducing fibers into the subscriber network

    Page(s): 1667 - 1675
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    Two approaches to fiber-optic subscriber loop system development in Japan are described. In the first. Approach I, NTT aims at introducing inexpensive fiber-optic subscriber loop systems using conventional LED's, multimode fiber, and analog transmission techniques in the near future. In the second, Approach II, fiber-optic subscriber loop systems will be made highly functional by evolving from analog to digital transmission. This paper presents system fabrication examples for each approach and the results obtained in the tests. View full abstract»

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Aims & Scope

The Journal of Lightwave Technology contains articles on current research, applications and methods used in lightwave technology and fiber optics.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Peter J. Winzer
Alcatel-Lucent Bell Labs