By Topic

Lightwave Technology, Journal of

Issue 6 • Date Jun 1992

Filter Results

Displaying Results 1 - 20 of 20
  • A comparison of Lanczos electric field propagation methods

    Publication Year: 1992 , Page(s): 772 - 776
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (412 KB)  

    The authors analyze the losses of a strongly guiding semiconductor rib waveguide Y-junction with the aid of various propagation algorithms based on Lanczos reduction. Although for the example Lanczos procedures adequately describe electric field propagation in the Fresnel approximation, the Helmholtz implementation converges unacceptably slowly. They therefore propose a finite-difference wide-angle approach which employs a power-series expansion of the forward propagation operator. The computational efficiency of the method is comparable to that of the Fresnel formalism with little or no reduction in accuracy from the Helmholtz technique View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Rare-earth doped optical fibers for temperature sensing

    Publication Year: 1992 , Page(s): 847 - 852
    Cited by:  Papers (7)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (396 KB)  

    The feasibility of using a variety of rare-earth doped optical fibers for measuring spatially averaged temperatures from ~0 to ~100°C over distances of 10 to 20 m is discussed. Such distributed temperature sensors would be particularly well-suited for building climate control systems and industrial processing applications. The temperature-dependent absorption spectra of 6 MCVD processed fibers containing different concentrations of Nd3+, Pr3+, and Yb3+ rare-earth ions were characterized and used to determine thermally active dopant species, optimal dopant concentrations, and most sensitive operating wavelengths for use as dual wavelength distributed temperature sensors View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • An efficient multilevel coherent optical system: M-4Q-QAM

    Publication Year: 1992 , Page(s): 777 - 786
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (744 KB)  

    A coherent multilevel transmission system based on the modulation of all the optical field degrees of freedom (the four quadratures of the optical field) is presented. The transmitted symbols are represented in the space of the field quadratures by a square lattice of points, so that both the transmitter and the decision devices can be easily implemented. The proposed modulation formats allow high spectral efficiency systems to be designed without paying a great sensitivity penalty with respect to binary systems. For this reason the proposed modulation format seems promising for application in densely spaced very-high-capacity FISM networks and in high-speed data transmission in parallel computers View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Frequency multiplexing of remote all-fiber Michelson interferometers with lead insensitivity

    Publication Year: 1992 , Page(s): 853 - 863
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (752 KB)  

    A scheme to frequency multiplex a group of sensors based on all-fiber Michelson interferometers is presented. Lead insensibility is obtained by using the two fiber leads of the configuration as an extra Michelson interferometer whose differential phase is kept constant by active compensation. Topics concerning the system design, sensor sensitivity, and crosstalk between sensors are investigated. Experimental and numerical computational results are presented View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Variational analysis of single-mode inhomogeneous planar optical waveguide

    Publication Year: 1992 , Page(s): 747 - 752
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (428 KB)  

    Some trial fields are proposed for obtaining the propagation characteristics of single-mode inhomogenous planar waveguides, based on the scalar variational principle. A comparison with other trial fields and the exact numerical results shows that the authors' results are more accurate than those obtained by the existing trial fields. The proposed trial fields also agree favorably with the real inhomogeneous index profiles View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Frequency domain analysis of an optical FM discriminator

    Publication Year: 1992 , Page(s): 787 - 793
    Cited by:  Papers (25)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (648 KB)  

    Measurement of optical phase and frequency deviations using a frequency-domain network analysis approach is described. The frequency domain transfer functions are given which relate the conversion of optical phase, frequency, and intensity modulation into photodetector current after passing through a quadrature biased Mach-Zehnder interferometer. It is shown that the error term in the phase and frequency transfer functions depends only to second order on any accompanying intensity modulation. Experimental data are given illustrating the analytical results View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • An LiNbO3 integrated coherence modulator

    Publication Year: 1992 , Page(s): 760 - 766
    Cited by:  Papers (12)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (620 KB)  

    The authors describe the principle of operation and the performance of a newly integrated LiNbO3 modulator specially designed to generate optical delays of several millimeters. This is achieved by using the simultaneous propagation of the TE and TM modes in a waveguide and by taking benefit of the high natural birefringence of LiNbO3. This modulator is well-suited to coherence modulation of light in fiber-optic transmissions. When powered by a short coherence source, the large optical delays induced by a cascade of such modulators can be used as information carriers to transmit several signals simultaneously. A demonstration is reported using a single source and two modulators in cascade to transmit signals simultaneously View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Analysis of the automatic frequency control in heterodyne optical receivers

    Publication Year: 1992 , Page(s): 794 - 803
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (712 KB)  

    A theoretical analysis of the automatic frequency control (AFC) in binary DPSK and FSK heterodyne optical receivers is presented, and its impact on the system performance is evaluated. The effects of the shot-noise AM/FM conversion in the frequency discriminator are analyzed. It is shown that with commercial DFB lasers a common analysis of the frequency control loop can be done for the three modulations considered. Design guidelines are given that account for the presence of the AFC loop by properly using some performance results derived in the assumption of perfect frequency tracking View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Optimal source linewidth in a coherence multiplexed optical fiber communications system

    Publication Year: 1992 , Page(s): 804 - 810
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (564 KB)  

    In a fiber-based coherence multiplexed (CM) system, fiber path lengths must be carefully controlled. In an extrinsic reference ladder (ERL) CM system, two optical fibers are required to connect the transmitter array to each receiver. The effect of differential length variations between these two fibers is examined and is found to have significant impact on carrier-to-noise ratio (CNR). It is determined that, for a given differential mismatch length, there is an optimum value of optical source linewidth which maximizes system multiplexing capacity. An expression for the SNR of a certain multichannel digital CM communications system is developed View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Numerical analysis of InP/InGaAsP ARROW waveguides using transfer matrix approach

    Publication Year: 1992 , Page(s): 767 - 771
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (376 KB)  

    The transfer matrix method is employed to analyze the modal propagation within planar InP/InGaAsP antiresonant reflecting optical waveguides (ARROW) at the operational wavelength of 1.55 μm. The numerical results provide an accurate picture of dispersion and attenuation of both TE and TM polarized waves. Spatial properties of the modes are also investigated and detailed plots of the variation of electric field amplitude with layer thickness are given View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A systems perspective on digital interconnection technology

    Publication Year: 1992 , Page(s): 811 - 827
    Cited by:  Papers (58)  |  Patents (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1688 KB)  

    The work describes, from a switching system designers perspective, present digital interconnection technologies and needs. The discussion begins at the chip-to-chip interconnection level and proceeds to the frame-to-frame level. The authors evaluate the optimal packaging and interconnection technology that should be used in future system designs. The analysis suggests that parallel optical data links based on a laser array technology implemented at the board-to-board level are presently advantageous. This analysis, as well as a detailed description of laser gate arrays, is also included View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Wavelength characteristics of (2×2) optical channel-type directional couplers with symmetric or nonsymmetric coupling structures

    Publication Year: 1992 , Page(s): 735 - 746
    Cited by:  Papers (5)  |  Patents (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (924 KB)  

    The wavelength dependence of waveguide-type directional couplers is investigated with respect to waveguide pattern symmetry in the coupling region. A rough approximation of the dependence is determined based on simplified transfer matrix multiplications, followed by a more detailed computer calculation using the beam propagation method (BPM). Wavelength-flattened coupling characteristics over a wide range, for example, from 1.33-1.55 μm, are predicted for several types of directional coupler with waveguide width asymmetry or a tapered width structure in the coupling region View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A WDM cross-connected star topology for multihop lightwave networks

    Publication Year: 1992 , Page(s): 828 - 835
    Cited by:  Papers (11)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (660 KB)  

    The authors propose a star topology for multihop lightwave networks in which the conventional N×N passive star coupler is replaced by fixed wavelength division multiplexed (WDM) cross connects. The proposed topology overcomes three major limitations of the conventional star topology. First, it reduces the number of wavelengths needed in a (p,k) ShuffleNet from kp k+1 wavelengths in the conventional topology to p wavelengths in the proposed one. Second, the signal power loss due to the 1/N power splitting at the star coupler no longer exists in the WDM cross connects and, therefore, the restriction on the supported number of users by the star network is alleviated. Third, it completely eliminates the need for wavelength filtering at the input to the receivers as is the case in the conventional star topology View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Effect of fiber coating on temperature sensitivity in polarimetric sensors

    Publication Year: 1992 , Page(s): 842 - 846
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (360 KB)  

    The effect of fiber coating on the temperature sensitivity in a polarimetric sensor has been investigated using the concept of finger prints for bare birefringent fibers. An accurate, simple mechanical model has been proposed for the analysis of phase sensitivity through stress analysis for multiply coated birefringent fibers. It is found that a singly coated fiber has a higher temperature sensitivity than a doubly coated fiber with a silicone buffer coating. Both singly and doubly coated birefringent fibers can have their temperature sensitivities nullified by choices of fiber coating View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Subscriber optical fiber cable transfer splicing system using mechanically transferable connectors

    Publication Year: 1992 , Page(s): 720 - 727
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (448 KB)  

    An optical fiber cable transfer splicing system is developed for use in removing or changing optical fiber cables. The system enables rapid transfer from existing optical fiber cables to newly installed ones. The transfer is carried out synchronously using two mechanically transferable connectors which terminate the optical fiber cables at two different points, such as manholes. Before the transfer splicing, the system identifies a fiber ribbon in order to avoid mistransfer. A transfer time of less than 30 ms was achieved. The fiber ribbon was identified with a loss, from an identification light source to an identification point, of 35.5 dB. With this system, cable transfer can be faultlessly carried out with only a slight interruption to working transmission systems and circuit quality degradation is suppressed View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Optical fiber couplers: scalar supermodes and polarization corrections

    Publication Year: 1992 , Page(s): 728 - 734
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (504 KB)  

    Scalar field corrections of first order in weak coupling are constructed for the supermodes of couplers composed of two identical step-index optical fiber cores by a novel perturbation technique. The perturbations of the propagation constants lead to the well-known result for the scalar coupling coefficient. However, from the corrected fields the direction-dependent polarization corrections are accurately calculated for the first time, yielding accurate results for both the form birefringence, and the polarization beam splitting View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • An efficient algorithm for determining the dispersion characteristics of single-mode optical fibers

    Publication Year: 1992 , Page(s): 705 - 711
    Cited by:  Papers (5)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (496 KB)  

    An efficient algorithm is proposed for calculating the dispersion characteristics of optical fibers with radially arbitrary refractive-index profiles. It is based on a variational finite-element formulation. Formulas for the derivatives of the normalized propagation constant w with respect to the normalized frequency V up to the second order are derived by using a reaction formula. These formulas contain the modal field ψ and its derivative dψ/dV. Two variational problems are then formed and solved as matrix equations by using the finite-element method. The first one is a conventional eigenvalue problem with eigen-solution {w,ψ} and dominates the computing time. The second one is a direct problem for dψ/dV and can be solved by a few simple matrix manipulations. The proposed algorithm turns out to be a rapidly convergent one and careful arrangement results in saving for both storing memory and computing time View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Performance of telecommunication-grade multimode fiber at 780 nm

    Publication Year: 1992 , Page(s): 712 - 719
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (712 KB)  

    Presents the physics of graded-index multimode fiber and test results that demonstrate 780-nm compact disc (CD) lasers operating at the high speeds (266 Mb/s) and moderate distances (~2 km) for data communications. The test results include fiber characterizations of bandwidth and attenuation, and system performance testing of bit error rate measurements and eye closure characterization. The predictability of 780-nm performance from existing characterization at the traditional wavelengths of 850 and 1300 nm is sufficiently precise to permit the conservativeness necessary for standardization. Telecommunication-grade 50-μm fiber is ideally suited to this application because commercial pressures have caused 62.5-μm fiber to be optimized for 1300-nm light emitting diode (LED) operation View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Influence of space charges on the impulse response of InGaAs metal-semiconductor-metal photodetectors

    Publication Year: 1992 , Page(s): 753 - 759
    Cited by:  Papers (19)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (712 KB)  

    The impulse response of interdigitated metal-semiconductor-metal photodetectors fabricated on an Fe-doped InGaAs absorbing layer and an Fe-doped InP barrier enhancement layer is investigated. For ultra-short pulse excitation of 150 fs at λ=620 nm the photoresponse is found to be less than 13 ps FWHM for detectors with 1 μm finger spacing. Above a certain level of illumination, the peak amplitude increases sublinearly and the relative contribution of the tail to the detector response is appreciably enhanced. The screening of the electric field by photo-generated space charges is responsible for this nonlinearity. For detectors with 5 μm finger spacing illuminated with 1.3 μm light pulses (FWHM=33 ps), space charge perturbation of the impulse response manifests itself by a decrease of the FWHM and an increase of the fall time with increasing illumination level. The practical consequences for the performance of MSM detectors in various applications are discussed View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Etched fibers as strain gauges

    Publication Year: 1992 , Page(s): 836 - 841
    Cited by:  Papers (5)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (540 KB)  

    A class of optical fiber intensity sensors that do not require the use of external structures to impose perturbations on fibers is presented. The topological structures are formed directly onto the fiber cladding. The geometry of the features is defined photolithographically and the structures are formed by chemical etching. The etched fiber sensing elements have been fabricated and tested as strain sensors. Depending on the amount of the cladding material removed and the symmetry of the etched structure, the measured gauge factor of the etched fiber strain sensors may be larger than 100. The responses of the optical fiber strain gauges are linear, repeatable, have a high cyclic endurance and no measurable hysteresis. These sensors can be used to monitor a strain as large as 0.4% View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.

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