By Topic

Lightwave Technology, Journal of

Issue 2 • Date Feb 1990

Filter Results

Displaying Results 1 - 21 of 21
  • Source-induced noise in optical systems driven by low-coherence sources

    Page(s): 183 - 189
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (612 KB)  

    High-power quasimonochromatic light sources may deliver enough power into optical and fiber-optic systems to make the source noise dominant at the system output. With an RMS value proportional to light intensity, this noise limits the system sensitivity and dynamic range to levels which cannot be improved by injecting more light into the system. Source-related noise may originate not only from the source intensity fluctuations, but also from a phase-to-intensity conversion process which is characteristic of many single-spatial-mode multiple-path optical systems. The shape of the power spectral density of the source-induced noise, being critically dependent on the physical structure of the system, is analyzed for a self-homodyne Mach-Zehnder structure and for a recirculating delay line. For single-path communication systems, it is shown that source-originated noise exceeds both shot and thermal noise for a received optical power of only a few tens of microwatts View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Modal dispersion and attenuation measurements of silicon nitride and silicon oxynitride waveguides using a streak camera

    Page(s): 235 - 238
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (328 KB)  

    By measuring short pulse propagation in silicon nitride and oxynitride waveguides fabricated on silicon, it has been possible to characterize both attenuation and group velocity dispersion accurately for the different modes that propagate. The method is self-calibrating, using the ratio between scattered light from forward and backward traveling pulses at a particular point on the waveguide. In principle, the group velocity data can be used to calculate the phase velocities for the different modes using known dispersion relations. The phase velocities were measured independently using a prism coupling technique, and the group velocities that could be derived from them matched the experimental data within a few percent. The resolution of the technique is limited mainly by amplitude fluctuations of the laser. The full-width-half-maximum resolution was at best about 12 ps but should be extendable to better than 5 ps View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • An algorithm for bit-skew correction in byte-wide WDM optical fiber systems

    Page(s): 239 - 242
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (296 KB)  

    Some objectives for a bit-skew correction system are presented. The properties of optical fiber transmission which allow realization of these objectives are discussed. It is shown that the bit-skew limitation due to chromatic dispersion in byte-wide wavelength division multiplexing (WDM) optical fiber systems can be corrected automatically with no prior knowledge of the fiber parameters or link length and that the full potential of such systems can be attained with circuitry which is no faster than the bit subchannel data rate. In addition, the absolute wavelengths of the sources are not required as long as the channel spacing is constant View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Cladding layer thickness-controlled directional coupler optical switch

    Page(s): 259 - 263
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (488 KB)  

    The AlGaAs/GaAs cladding layer thickness-controlled directional coupler optical switch (CTC-SW) is discussed. To increase the efficiency of coupling between two waveguides, the CTC-SW was designed with a thin i-AlGaAs cladding layer h between the two waveguides. The coupling length Lc can be reduced, without reduction of the extinction ratio and increase of the switching voltage. For instance, Lc of CTC-SW (h=0.07) can be reduced 40% more than that of a conventional directional coupler switch (h=0). The extinction ratio is near 20 dB, both for the crossover (applied voltage V=0 V) and straight-through (V =19 V) states. A technique for adjusting Lc to the device length was developed View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Bias-correlated branched-waveguide cascaded light intensity modulator in the scattering matrix formalism

    Page(s): 221 - 226
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (488 KB)  

    The authors describe the concept of a composite interferometric light intensity modulator constructed in the form of a cascade of 2n branched-waveguide electrooptic modulators in which the DC bias of the individual modulators are provided in a certain phasing required to yield a high overall modulation efficiency. The analysis of this cascaded modulator, presented in the scattering matrix formalism, predicts that the overall modulation efficiency of the cascade is increased by the factor 2n/2 compared with that of a single constituent modulator when both are supplied with the same amount of modulating signal power View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A distributed fiber optic sensor based on cladding fluorescence

    Page(s): 212 - 220
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (704 KB)  

    The fiber for the sensor is formed by cladding fused silica during drawing with polydimethyl siloxane into which an organic fluorescent dye, 9, 10-diphenylanthracene, has been dissolved. Upon side illumination at a wavelength within the excitation range of the dye, the cladding fluoresces; some of this fluorescence is coupled into guided modes in the fiber core through the evanescent fields of these modes. In the presence of oxygen, fluorescent emission by the dye is diminished. For the sensor described, the rubbery liquidlike nature of the polydimethyl siloxane cladding allows rapid diffusion of gases, and the intensity of the guided fluorescence is observed to drop by 30% in less than 5 s when the ambient atmosphere changes from pure nitrogen to pure oxygen. The advantages of this sensing technique, and some of the possibilities for new sensors based on this principle, are discussed View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Strategies and technologies for planning a cost-effective survivable fiber network architecture using optical switches

    Page(s): 152 - 159
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (788 KB)  

    A 1:1 diverse routing protection switching architecture using optical protection switches to reduce costs for providing 1:1 (i.e. 100%) protection against fiber cable cuts is proposed. A cost analysis model is used to evaluate cost/survivability merits for 1:1 optical diverse protection architectures. Results show that the best place to deploy the 1:1 photonic diverse protection architecture in future networks is in spans carrying large DS3 demands, which are usually interhub spans. The proposed architecture can be implemented using electronically controlled low-speed single-mode fiber mechanical optical switches as protection switches to meet current performance and availability requirements View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Fabrication of submillimeter-radius optical waveguide bends with anisotropic and isotropic wet chemical etchants

    Page(s): 264 - 270
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (844 KB)  

    Wet chemical etchants suitable for making GaAs/AlGaAs single-mode optical waveguide bends with radii as low as 300 μm for excess bend losses of 1 dB/90° and propagation losses as low as 1 dB/cm at λ=1.5 μm are described. Additional bend losses due to modal mismatch resulting from etchant anisotropy are investigated, and it is shown that in many cases such anisotropy does not limit bend performance View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Design parameters of Ti:LiNbO3 waveguides for optimum acoustooptic interaction efficiency

    Page(s): 168 - 172
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (472 KB)  

    A computer model of optical and surface acoustic wave modes in titanium indiffused Y-cut LiNbO3 guiding structures is used to produce several graphs for the design of guided-wave acoustooptic devices with optimum interaction characteristics. The design concentrates on waveguide fabrication parameters in order to achieve the optimum acoustic frequency and the acoustooptic interaction bandwidth. The optimum acoustic frequency for a given value of Ti film thickness and diffusion depth is defined as the frequency causing the maximum value of the overlap integral View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 2.24-Gbit/s 151-km optical transmission system using high-speed integrated silicon circuits

    Page(s): 227 - 234
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (952 KB)  

    Optical transmission experiments performed at 2.24 Gb/s using standard single-mode fiber with dispersion zero at 1.3 μm are discussed. In the optical transmitter, a 1.5-μm-wavelength distributed feedback laser is directly modulated by means of a special electrical drive pulse shaping technique. A link length of up to 151 km is bridged. This is the longest repeater distance at 2 Gb/s using direct detection without optical amplifiers reported so far. Moreover, the transmission system includes multiplexing and demultiplexing equipment using specially developed high-speed silicon integrated circuits. The whole system is assembled in a version suitable for field trial applications View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Splice loss between different Gaussian-elliptic-field single-mode fibers

    Page(s): 173 - 176
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (200 KB)  

    Splice losses between two different Gaussian-elliptic-field single-mode fibers are derived under various mechanical misalignment conditions. Loss values for azimuthal rotation (Lφ ), transverse offset (Ld), and axial tilt (Lθ), as well as some of their combinations, are calculated under typical parameter range. Linear combination of L φ and Ld may cause considerable error, while Lφ could be considered as independent from Lθ with fairly good accuracy. Comparisons with previous works reveal some errors in the latter case View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • On the analysis of optical fibers described in terms of Chebyshev polynomials

    Page(s): 164 - 167
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (228 KB)  

    An analysis is made of an optical fiber whose arbitrary refraction function is expressed in terms of the Chebyshev polynomials. The method of separation of variables is used for solving the corresponding wave equation. As the general solution of this equation, the series with undetermined coefficients and the same kind of Chebyshev polynomials is obtained. These undetermined coefficients are calculated on the basis of the corresponding coefficients of the assumed refraction function. It is shown that the proposed analysis algorithm is accurate, fast convergent, and reliable from the standpoint of numerical calculations. The validity of the presented approach and analysis algorithm has been confirmed by a numerical experiment View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Analysis of fiber directional couplers and coupler half-blocks using a new simple model for single-mode fibers

    Page(s): 143 - 151
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (708 KB)  

    A model for a step-index fiber in the form of an equivalent slab guiding structure is presented. This model simplifies the analysis of fiber directional couplers and coupler half-blocks with dielectric and metallic superstrates. Simple empirical formulas to obtain the model parameters are also given. The use of this model is illustrated with some numerical examples View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Polarization rotation in nonlinear bimodal optical fibers

    Page(s): 129 - 137
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (632 KB)  

    The effect of nonlinear interactions on second-order modes in circular cross-section optical fibers is considered. In the linear case, analysis using the proper modes reveals that the fiber is a natural polarization rotator. An initial linearly polarized (LP) mode is actually a mixture of proper modes and recurs only periodically as the field propagates; at half-periods the input polarization and field pattern are rotated by 90°. Complete analytical expressions and numerical examples describing the modification of this phenomenon by nonlinearity are presented. For lower powers, the phenomenon persists with period increasing toward infinity at a transition point, beyond which complete polarization rotation is suppressed. At very high powers, the Kerr effect dominates: polarization is fixed in one direction and an LP mode does become a real mode of the system View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Multichannel wavelength-switched transmitters and receivers-new concepts for broadband networks and distributed switching systems

    Page(s): 202 - 211
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (816 KB)  

    Three component concepts for use in high-density wavelength-division-multiplexed optical systems are described. The applications envisaged for these components include broadband overlay for subscriber access networks and ultrahigh-capacity packet switching for telecommunications or parallel processing computer applications. The components each use a dispersive optical grating and integrated array of optoelectronic transducers to form a component with precisely defined multiple operating wavelength channels. Multichannel laser transmitter and direct detection receiver components suitable for up to about 50 independent channels separated by 1-2 nm in the 1300- to 1600-nm-wavelength range are described View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Simultaneous measurement of temperature and strain: cross-sensitivity considerations

    Page(s): 138 - 142
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (516 KB)  

    Interferometric sensors using optical fibers as a transduction medium have been shown to be sensitive to a variety of physical measurands. A result of this is that the resolution of a system designed to sense strain, for example, may be compromised by fluctuations in the temperature of the environment. The possibility of simultaneously determining the strain and temperature applied to the same piece of highly birefringent fiber is discussed. Second-order effects are shown to be important for long sensing lengths or in the presence of high strains or temperature changes. The results of experiments carried out to verify the theoretical predictions are also described View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Double-layered magnetooptic channel waveguide for waveguide isolator application

    Page(s): 177 - 182
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (564 KB)  

    TE-TM mode conversion based on the nonreciprocal Faraday effect for waveguides fabricated by liquid-phase epitaxially grown (YBiCa)3Fe5O12 films is discussed. The phase mismatch is controlled by constructing a double-layer channel waveguide with an intermediate cladding layer of refractive index slightly lower than the core. Care must be taken to compensate any birefringence of materials, e.g. stress- and growth-induced birefringence. It is shown that such a structure is effective in decreasing the effect of waveguide shape deformation on the phase-matching degree. The analysis of the double-layered channel waveguide and experimental results are described View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Optimum system design for CPFSK heterodyne delay demodulation system with DFB LDs

    Page(s): 251 - 258
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (636 KB)  

    An optimum system configuration for an optical continuous-phase frequency-shift-keying (CPFSK) heterodyne delay demodulation system with distributed feedback laser diodes (DFB LDs) is discussed. The optimum modulation index was determined by evaluating the LD phase noise effect and the IF noise effect. The IF noise effect was investigated in detail, considering the noise conversion effect through delay demodulation. In the case of 10-MHz IF beat spectral width, the modulation index m =1.5 is optimum for a 1.2-Gb/s system. With this optimum modulation index, a 204-km long-span transmission experiment, with -41.5 dBm receiver sensitivity, has been successfully performed. The feasibility of using stand-alone DFB LDs for a high-sensitivity CPFSK delay demodulation system has been confirmed through this experiment View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Phase-noise-canceled differential phase-shift-keying (PNC-DPSK) for coherent optical communication systems

    Page(s): 190 - 201
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (984 KB)  

    A modulation scheme using a nonlinear demodulation process, phase-noise-canceled differential phase-shift keying (PNC-DPSK), is used to circumvent the effects of phase noise in a phase-shift keying (PSK) system. A theoretical description of the system is given, and results of an experimental test system are shown to be in good agreement with the predictions. In particular, it is shown that the phase-noise-induced bit error rate (BER) floor can be eliminated despite using lasers with linewidths comparable to the data rate. Furthermore, for an optimized PNC-DPSK system, the degradation at high signal-to-noise compared to heterodyne PSK with ideal sources (i.e. no phase noise) should only be ≈3 dB View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • An optical FSK heterodyne dual filter detection system for taking advantage of DFB LD applications

    Page(s): 243 - 250
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (764 KB)  

    An optimum system configuration for an optical frequency-shift keying (FSK) heterodyne dual-filter detection system with distributed feedback laser diodes (DFB LDs) is investigated, taking into consideration LD phase noise influence. Experimental and theoretical examination show that an IF filter bandwidth greater than 10 times the beat spectral linewidth is necessary to avoid LD phase noise influence. A 301-km long-span transmission experiment has been successfully carried out with an optimum configuration for 34 Mb/s. High receiver sensitivity, -61.8 dBm with more than 10 dB improvement over the direct detection system, has also been achieved. Experimental results at higher bit rates of 140, 200, and 280 Mb/s indicate that a modulation index greater than two is desirable to avoid cross talk between mark and space signals. With sufficient frequency deviations, high receiver sensitivities of -54.7 dBm (140 Mb/s) and -52.5 dBm (200 Mb/s) have been achieved. These represent 9.6- and 9-dB sensitivity improvement, respectively, over direct detection systems. A guide for FSK dual-filter detection system design is derived from the experimental and theoretical results. Potential application regions for a dual-filter detection system with DFB LDs are determined View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Polarization-independent LiTaO3 guided-wave electrooptic switches

    Page(s): 160 - 163
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (388 KB)  

    Polarization-independent LiTaO3 optical switches that utilize the off-diagonal electrooptic coefficient r51 are discussed. The waveguides are formed by Zn vapor diffusion. Interguide transfer efficiencies of 84 and 88% for TM and TE polarizations, respectively, have been obtained. Modulation efficiency of 99.8% for TM and 95% for TE have been demonstrated at nearly equal voltages by thermally tuning to 20°C. The relatively high voltage-length product (30-35 V-cm) attained in these initial devices at a 0.633-μm wavelength is attributed to a weak overlap between optical and electrical fields in the periodic electrode structure 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