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Lightwave Technology, Journal of

Issue 8 • Date Aug 1993

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Displaying Results 1 - 18 of 18
  • Microwave properties of traveling-wave electrodes in LiNbO3 electrooptic modulators

    Publication Year: 1993 , Page(s): 1274 - 1278
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (364 KB)  

    The microwave characteristics of a traveling-wave electrode in electrooptic modulators on z-cut LiNbO3 crystals with buffer layers with various dielectric constants are calculated by a quasi-TEM analysis. The theoretical results are compared with the measured results on z-cut crystals for coplanar waveguide (CPW) electrodes. The agreement between the calculated and the measured results is good View full abstract»

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  • Analysis of a damage sensor based on elastic-plastic metal coatings on optical fibers

    Publication Year: 1993 , Page(s): 1385 - 1393
    Cited by:  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (744 KB)  

    Optical-fiber sensors coated with linear work hardening elastic-plastic materials are analytically explored to determine the effects the coating properties have on the sensor performance. The optical-fiber system is analytically subjected to both an axial load and a uniform thermal gradient. The nonlinear analysis reveals a mechanism for designing coatings which provide a memory to the optical-fiber sensor by undergoing permanent deformations in response to large thermal or mechanical strain excursions. This behavior is exploited to design a damage sensor View full abstract»

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  • Quantum limited noise figure operation of high gain erbium doped fiber amplifiers

    Publication Year: 1993 , Page(s): 1344 - 1352
    Cited by:  Papers (1)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (892 KB)  

    Performance improvements obtained by using an isolator as an amplified-spontaneous-emission-suppressing component within erbium-doped fibers are evaluated. Simultaneous high-gain and near-quantum-limited noise figures can be obtained by such a scheme. The noise figure improves for input signal powers below -5 dBm, and an improvement of 2.0 dB with a simultaneous gain increase of 4.1 dB is measured relative to a gain-optimized fiber. The optimum isolator location is evaluated for different pump and signal wavelengths in both an Al/Er-doped and a Ge/Er-doped fiber, for pump and signal power variations and different pump configurations. In all cases the optimum isolator position lies within 10-37% of the total fiber length for small signal operation View full abstract»

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  • Continuously tuned external cavity semiconductor laser

    Publication Year: 1993 , Page(s): 1279 - 1286
    Cited by:  Papers (5)  |  Patents (76)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (612 KB)  

    Continuous tuning (no mode hops) of a grating-tuned external-cavity semiconductor laser by rotation of the grating about a carefully selected point is analyzed and demonstrated using a laser containing a prism beam expander. The analysis predicts the continuous tuning range as a function of pivot-point position and is used to select the point for maximum continuous tuning range. Because dispersive optical elements in the cavity were found to limit the continuous tuning range, the model was modified to include dispersion to first order. The dispersion correction improved the maximum observed tuning range of the 1300-nm-wavelength laser from 600 GHz to nearly 3000 GHz. Details of the cavity and mechanical design as well as pivot-point tolerances are also included View full abstract»

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  • Performance of the PAC optical packet network

    Publication Year: 1993 , Page(s): 1394 - 1399
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (552 KB)  

    For multiuser packet communications with unpredictable user demands (e.g., in a local or metropolitan area network), coordination and control of access to the frequency-division multiplexing (FDM) channels are difficult. B. Glance (J. Lightwave Technol., vol.10, pp.1323-1328, Sep 1992) proposed using a simple protection-against-collision (PAC) circuit to solve this media access problem and achieve full optical connectivity. The PAC system has the potential to interconnect hundreds of ports, each transmitting at several gigabits per second. Performance aspects of the PAC optical packet network are discussed here. The delay-throughout performance of this network is analyzed for uniform traffic patterns. The results show that in geographically distributed applications the maximum achievable throughput (normalized to the transmission rate) is typically between 0.4 and 0.5 per channel. In a centralized switch the (normalized) maximum achievable throughput can approach 0.8 per channel View full abstract»

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  • On the validity of the effective-index method for rectangular dielectric waveguides

    Publication Year: 1993 , Page(s): 1320 - 1324
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (400 KB)  

    The effective-index method (EIM) for rectangular dielectric waveguides is derived as an approximation from an exact equivalent-network formulation. It is explained why EIM gives accurate results for the fundamental modes in near cutoff region as well as for all the guided modes in well-guiding region. As a direct improvement on EIM a simple eigenvalue equation is presented, which takes into account the shape of the predominant slab-waveguide mode. It is shown that EIM overestimates propagation constants compared to the improved results View full abstract»

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  • Rigorous analysis of coupling between laser and passive waveguide in multilayer slab waveguide

    Publication Year: 1993 , Page(s): 1353 - 1359
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (436 KB)  

    An approach that combines the finite-element and boundary-element methods (FEM/BEM) is extended to the analysis of arbitrarily shaped discontinuities in a multilayer slab waveguide. Here all the eigenmodes, namely, guided modes, substrate radiation modes, and substrate-cover radiation modes, are taken into account and are constructed by an extended matrix method. Computed results are given for the rigorous analysis of the coupling between a five-or six-layer laser and a four-layer passive waveguide in a monolithically integrated circuit. Some of the results are for multimode incidence. Since the coupling is one of the most important discontinuity problems in practice, this result confirms the usefulness of the approach View full abstract»

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  • Semiconductor laser amplifier as optical switching gate

    Publication Year: 1993 , Page(s): 1287 - 1295
    Cited by:  Papers (24)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (848 KB)  

    The properties of a semiconductor laser amplifier as optical switching gate are investigated. Particular attention is paid to gain, contrast ratio, and switching time of the device. These properties are studied experimentally and theoretically with respect to the injection current, optical input power, and cavity resonances. The experimental arrangements and the theoretical method are described. As an example of the various applications of semiconductor laser amplifier gates, packet switching experiments with self-routing, employing cascaded switching gates, are reported. In a theoretical analysis the restrictions that the properties of semiconductor laser amplifier gates impose on a larger switching system consisting of many such gates are investigated View full abstract»

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  • Design considerations for vertical δk directional coupler

    Publication Year: 1993 , Page(s): 1331 - 1336
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (528 KB)  

    Theoretical results relevant to the design of a vertical Δκ switch are presented. The principle of a Δκ switch is the modulation of the coupling length by the application of an even electrooptic perturbation on the coupling region. Power switching requires that ΔκL=π/2. The initial state can be tuned electrically. The coupling length and the change with the index perturbation depend on many factors, such as the thickness and the refractive index of the coupling layer. Based on an analytic solution of the eigenmodes and eigenindices of the symmetric structure, the author clarifies many of these dependencies and obtains the relationship between the switching length required for power crossover and the available index change. The merits of the Δκ switch are discussed, and its efficiency is compared with that of the conventional Δβ switch View full abstract»

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  • Guided-wave optical equalizer with α-power chirped grating

    Publication Year: 1993 , Page(s): 1325 - 1330
    Cited by:  Papers (1)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (456 KB)  

    A theoretical investigation of a guided-wave optical equalizer with an α-power chirped grating is presented. A group delay dispersion of 3700 ps/nm can be obtained at λ=1.55 μm by a chirped grating with α=0.3. It is shown that the chromatic dispersion of 200 km of a fiber whose zero-dispersion wavelength is located at 1.3 μm can be compensated at 1.55 μm to achieve up to 10 GHz signal bandwidth View full abstract»

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  • Coherent frequency-domain reflectometry for characterization of single-mode integrated-optical waveguides

    Publication Year: 1993 , Page(s): 1377 - 1384
    Cited by:  Papers (38)  |  Patents (84)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (712 KB)  

    Based on the principles of optical frequency domain reflectometry (OFDR), a highly resolving and sensitive technique suitable for detecting, localizing, and quantifying weakly reflecting irregularities in single-mode optical waveguides is developed. A distributed feedback (DFB)-laser diode at λ0≅1.3 μm tuned within a range of Δλ≅6 nm and Δv≅1 THz, respectively, is used as a source in the experimental arrangement. An auxiliary interferometer is employed so that the tuning need not be linear in time, in contrast to early implementations. At present, with waveguide structures on InP under test, a spatial resolution of 50 μm and a dynamic range of about 60 dB are obtained. These data surpass OFDR results published so far. Prospects of closing the gap to coherence-domain reflectometric results and specific advantages make OFDR a promising technique View full abstract»

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  • Performance parameters of a wavelength-division demultiplexer made with a single 3×3 coupler optical fiber ring or loop resonator

    Publication Year: 1993 , Page(s): 1337 - 1343
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (468 KB)  

    The performance parameters of a two-channel demultiplexer made with a single 3×3 coupler fiber ring or loop resonator are evaluated theoretically. These parameters include crosstalk, output intensity of the selected channel, and channel separation. Their dependence on the parameters of the coupler and the fiber such as the coupling length of the coupler, kd, the phase change of the fiber delay line, θ, and the round-trip amplitude transmission coefficient of the fiber ring or loop G, which is the product of the amplitude transmission coefficients of the coupler and the fiber delay line and the amplitude gain of the degenerate two-wave mixing, is investigated. It is found that the best performance can be obtained at G=1 View full abstract»

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  • Design of aplanatic waveguide Fresnel lenses and aberration-free planar optical systems

    Publication Year: 1993 , Page(s): 1314 - 1319
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (504 KB)  

    A modification of the waveguide Fresnel lens design that has phase-shifting zones placed on the curved contour is suggested. It is shown that the selection of a suitable shape for this contour allows coma aberration to be eliminated. Computer simulation results are presented to demonstrate the significant improvement of the optical characteristics for curved contour lenses. The aplanatic homogeneous refracting waveguide lenses are also considered. It is found that thick aplanatic refracting lenses and the proposed Fresnel lenses have field curvature aberration of opposite sign. This fact allows planar optical systems free from low-order aberration to be designed by combining refracting and Fresnel lenses. An algorithm for producing such a system is presented View full abstract»

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  • LiNbO3 waveguide quasi-phase-matching second harmonic generation devices with ferroelectric-domain-inverted gratings formed by electron-beam scanning

    Publication Year: 1993 , Page(s): 1360 - 1368
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (888 KB)  

    The characteristics of the formation of LiNbO3 ferroelectric-domain-inverted gratings using electron-beam scanning are examined and discussed for application to waveguide quasi-phase-matching second-harmonic-generation (SHG) devices. It is found that the domain inversion tends to occur in segmented regions, and the inversion width is thinner near the crystal surface than inside the crystal. The dependence of the SHG efficiency on the grating structure is examined theoretically. Prototype devices for green and blue light generation have been fabricated and the device performance examined. Normalized SHG efficiencies as high as 50%/W and 70%/W, respectively, are obtained in green and blue light generation devices of 3.3-mm length. The experimental results are compared with the theoretical results View full abstract»

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  • Monolithic integration of optical waveguide circuitry with III-V photodetectors for advanced lightwave receivers

    Publication Year: 1993 , Page(s): 1296 - 1313
    Cited by:  Papers (25)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1744 KB)  

    Recent progress in monolithic waveguide-photodetector integration on III-V semiconductors for applications in the 0.8-1.6-μm wavelength range is reviewed. Critical issues for device performance and fabrication are discussed, followed by a description of the underlying optical coupling mechanisms. Tradeoffs between performance and integrability are assessed in detail for vertical and butt coupling and their variants. It is shown how appropriately chosen integration techniques have led to a variety of monolithic devices for advanced lightwave receivers View full abstract»

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  • Estimated performance of 2.488 Gb/s CPFSK optical non-repeatered transmission system employing high-output power EDFA boosters

    Publication Year: 1993 , Page(s): 1369 - 1376
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (672 KB)  

    The configuration of a practical nonrepeatered coherent optical transmission system and its performance are reported. The practicability of combining continuous-phase frequency-shift keying (CPFSK) with erbium-doped fiber amplifier (EDFA) boosters is verified by laboratory and field experiments. A system gain of 60.8 dB is achieved at a BER at 10-11; the EDFA's optical output power is +18 dBm and the receiver sensitivity is -42.8 dBm. The stimulated Brillouin scattering (SBS) effect is examined to estimate the dependence of error rate characteristics on the bit sequence length. No power penalty is observed for a pseudorandom bit sequence (PRBS) of more than 25-1 or STM-16 patterns containing a 30-byte block of consecutive identical digits. The power penalty of 1.3 dB caused by the 310-km non-dispersion-shifted transmission fiber is successfully compensated by installing a chromatic dispersion compensator in each orthogonal polarization branch. During a four month field experiment, error-free operation was observed over a 30 day period, and the long-term error rate is under 6×10-16 View full abstract»

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  • Refractive-index profile influences on mode coupling effects at optical fiber splices and connectors

    Publication Year: 1993 , Page(s): 1270 - 1273
    Cited by:  Papers (5)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (252 KB)  

    An approach for calculating the mode conversion coefficients at optical fiber splices and connectors for any kind of fiber refractive-index profiles is developed. The method takes account of the azimuthal properties of modes which play an important role in the mode coupling phenomena. The approach can be also used to evaluate the splice losses in single-mode fibers View full abstract»

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  • Integrated-optic implementation of a confocal scanning optical microscope

    Publication Year: 1993 , Page(s): 1400 - 1403
    Cited by:  Papers (1)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (496 KB)  

    A confocal scanning optical microscope implemented in an integrated-optic structure is demonstrated. The compact nature of the device proves to be more suitable for environments where mechanical shock can result in optical misalignment of discrete components. The device is implemented in a thin-film optical waveguide with optical fiber connections for light input and output. An objective lens and focusing beam splitter are incorporated into the waveguide structure to form the sensing head of the microscope. The fabrication of the device is discussed, and both intensity and differential contrast images are presented to demonstrate the device operation. The confocal imaging characteristics of the microscope are also demonstrated 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.

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Meet Our Editors

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