Journal of Lightwave Technology

Among SONET ring alternatives, the four-fiber bidirectional self-healing ring architecture (BSHR/4) has the highest available capacity and can work with today's systems with minimum change. A cost-effective implementation for a BSHR/4 which uses a totally passive ring as the protection ring of the BSHR/4 is presented. The ring uses a SONET ring to carry working traffic and a passive ring to carry ... View full abstract»

A thorough and detailed characterization of annealed proton-exchanged (APE) waveguides in Z-cut LiNbO3 is described. The mode index measurements in planar waveguides as a function of wavelength and annealing time are reported, including useful analytical relations for the refractive index change, its dispersion, and the depth profile as a function of annealing parameters. Analy... View full abstract»

A study of the fabrication and optical properties of planar waveguides fabricated in MgO:LiNbO3 and LiNbO3 substrates by diffusion of a ZnO film is presented. Transmission electron microscopy was used to show that using ZnO instead of metallic zinc as a source, and maintaining the ZnO film thickness below a prescribed value, greatly reduces second phase precipitation and prod... View full abstract»

When coherent light is coupled into a multimode waveguide (such as a fiber), a speckle pattern is formed at the fiber output. When the fiber is vibrated, the speckle pattern is modulated due to mode coupling and phase modulation of the waveguide modes. It is shown that when a highly coherent light source is used, the speckle pattern modulation is due primarily to phase modulation of the modes. Whe... View full abstract»

It is shown that Lanczos reduction can be employed to analyze reflection at the interface between two inhomogeneous refractive index media. Although generally less accurate than split-operator techniques, the method is convergent for a relatively small number of Lanczos functions if modes with near cutoff propagation constants are not appreciably excited. A substantial compensating advantage in co... View full abstract»

A receiver concept based on optical quadrature phase-shift keying (QPSK) and a digital realization of synchronous demodulation including phase synchronization is presented. To keep the signal processing bandwidth low a phase diversity receiver, called an intradyne receiver, with an orthogonal electrical demodulation is proposed. Basic principles of the synchronous orthogonal and digital demodulati... View full abstract»

The propagation of Gaussian beams in both a homogeneous medium and a lenslike medium is treated. The correct Helmholz equation derived by the author is used to obtain the analytic solutions, taking into account the diffraction effect. Based on this, the beamwidth and the form of the wavefront are considered. The beamwidth will increase monotonically in the homogeneous medium and will be sinusoidal... View full abstract»

The performance of distributed feedback (DFB) structures fabricated on ion exchanged waveguides has been numerically analyzed. Waveguide exchange time, grating order, period, number of periods, grating shape, and grating depth have been included as variables for the analysis. The results are for K⁺-Na⁺-type systems exchanged at 385°C View full abstract»

A method based on coupled mode theory for numerical simulation of three-dimensional structures is presented. It can be applied to all coupling structures for which the interaction with radiation modes is unimportant and distortions of the fields due to waveguide curvature are small. It treats the device cross section by a two-dimensional finite-difference algorithm, thus avoiding the limitations a... View full abstract»

Measured and calculated crosstalk ratios as a function of wavelength are compared for proton exchanged and annealed LiNbO3 directional couplers at λ=1550 nm. The analytical technique employed models the experimentally determined wavelength sensitivities reasonably well. The analytical technique is further used to predict comparable functions for titanium indiffused couplers, and... View full abstract»

The overall gain of a chain of erbium-doped fiber amplifiers in a long-haul all-amplifier system would be automatically stabilized if each amplifier were operated slightly into saturation. However, with the required low level of amplifier output power which is imposed by nonlinearity in the transmission fiber, the resulting pump power becomes too low to effectively invert the gain medium of the am... View full abstract»

An optically transparent packet network controlled by a simple medium access circuit is presented. The system, based on frequency division multiplexing and tunable transmitters, has no internal blocking and is optically self-routing. It provides internal collision-free traffic by allowing access to the network only if the addressed channel (output port) is available. A packet denied access to the ... View full abstract»

Compensation of light source chirping and optical fiber dispersion using semiconductor laser amplifiers (SLAs) is investigated using a modeling equation that describes the opposite phase characteristics of light sources to SLAs with self phase modulation. A two-section SLA was fabricated in order to achieve an amplifier with both high gain and phase compensation properties. Preliminary experimenta... View full abstract»

To determine the dispersion characteristics of nonlinear single-mode optical fibers, the various orders of derivative of the propagation constant with respect to frequency must be calculated. Recent studies have shown that high nonlinearity changes the guided modal field and then modifies the chromatic dispersion characteristics. However, the methods used either were approximate or were based on r... View full abstract»

A polarization-independent quasi-optical circulator having high isolation over a wide wavelength range is reported. The proposed quasi-circulator is composed of two polarization beam splitters, two pentagonal prisms, two nonreciprocal rotators, and two walkoff polarizing beam splitters. Its structure is very simple. A three-port quasi-circulator has been fabricated with single-mode fibers. Its ins... View full abstract»

An optical circulator configuration that does not use polarization beam-splitters (PBSs) is described. Birefringent crystals (BCs) are used instead of PBSs to achieve a high-isolation polarization-insensitive optical circulator. The use of BCs simplifies fabrication. A conceptual configuration and two concrete structures are proposed. The prototype optical circulator was tested and exhibited over ... View full abstract»

Field stitching errors and their effect on the single-mode characteristics of distributed feedback (DFB) lasers fabricated using electron beam lithography were investigated. The stitching errors are associated with small-area, high-resolution electron beam exposure, which has the potential advantage of high-speed writing of laser gratings. Measurements show that the errors are composed of a system... View full abstract»

A technique based on Brillouin gain spectroscopy is proposed to evaluate tensile and compressive strain variation in optical fibers. This technique is applied to characterize fiber strain in bent slot-type optical-fiber cables. Fiber ribbons containing four optical fibers each are stranded through the cable. When the cable is bent, two types of strain are created in the fiber. It was found from ex... View full abstract»

The effect of the external optical feedback on the 1.5-μm distributed feedback (DFB) laser's device and system performance, both unpackaged and packaged, is studied, considering reflection magnitudes, polarizations, and phases. The reflection is introduced into the laser's AR-coated facet and thus resembles the real system condition for both CW and pulsed (modulated) operations. It is demonstra... View full abstract»

A great improvement in the high-speed characteristics for compressively strained multi-quantum-well (MQW) distributed-feedback (DFB) lasers with self-aligned constricted mesa structures is described. Negative wavelength detuning is an important factor in making possible the extraction of potential advantages for the compressively strained MQW DFB lasers. A 17-GHz bandwidth, which is the highest am... View full abstract»