Journal of Lightwave Technology

Two important aspects of optical amplifier noise figure as measured with a heterodyne detection receiver are investigated. First, differential mode gain will result in polarization-dependent degradation of the perceived amplifier noise figure, even when the noise figures for the TE and TM modes of the amplifier are the same. For a differential mode gain of 7.5 dB the noise figure degradation can b... View full abstract»

The acoustic sensitivity of optical fibers is considered analytically. High sensitivity is obtained with low bulk modulus, very thick polymeric coatings. The fiber coatings play an important role in determining the fiber acoustic sensitivity. The very thick coating limit is realized by embedding optical fibers in an appropriate elastomer (polyurethane). A planar flexible fiber-optic interferometri... View full abstract»

The fiber-structure dependence of the gain characteristics of Er 3+ doped fibers pumped at 1.48 μm is analyzed. The optimum V value is derived theoretically and experimentally. For step-index fibers, the optimum V value is 1.6, which is smaller than that needed to minimize spot size. The fiber with a small V value enjoys a large Er3+ confinement ... View full abstract»

The limiting effects of four-wave mixing on optical frequency-division multiplexing (OFDM) systems are described. The optical nonlinearity in a single-mode fiber imposes a fundamental limitation on the capacity of optical frequency-division multiplexed systems. In particular, four-wave mixing (FWM) crosstalk may severely degrade the system performance when the fiber input powers are large and/or t... View full abstract»

Threshold current operation of 1.5 mA was achieved for 1.5-μm multiple-quantum-well distributed feedback (MQW-DFB) laser diodes (LDs) with semi-insulating current blocking layers entirely grown by metalorganic vapor phase epitaxy (MOVPE). Such low-threshold current is attained by reducing leakage current and mirror loss in the laser structure. The required bias current for achieving several gig... View full abstract»

A broadband optical waveguide star coupler with asymmetric directional couplers is proposed. A coupling or splitting ratio of the coupler is flattened with respect to wavelength by choosing appropriate values for Δβ and complete power transfer length. The wavelength characteristics of uniform and alternating Δθb directional couplers are investigated, and their broadband oper... View full abstract»

A theoretical and experimental study of an efficient technique for coupling a broad-area laser to a single-mode fiber without the use of bulk optical components was carried out. The technique uses a wedge-shaped fiber endface to approximate a cylindrical lens action to correct for the phase mismatch between the curved laser beam wavefront and the planar fiber beam. A theoretical formula for the co... View full abstract»

A 100-channel optical frequency-division multiplexing (FDM) transmission/distribution experiment at 622 Mb/s is demonstrated for a fiber length of 50 km. The feasibility of a polarization-insensitive waveguide frequency selection switch for 10-GHz intervals and a frequency-shift-keying (FSK) direct-detection scheme employing a Mach-Zehnder filter is verified. The demodulation circuit employs a Mac... View full abstract»

A comparison is presented of the performance of amplitude-shift-keying (ASK), frequency-shift keying (FSK), and differential-phase-shift-keying (DPSK) lightwave systems which operate at 10 Gb/s with directly modulated 1550-nm distributed feedback (DFB) laser transmitters and conventional 1310-nm dispersion-optimized fiber. Computer modeling techniques were used to accurately simulate the amplitude... View full abstract»

An optical-fiber crossbar switch has been constructed using fully integrated GaAs optoelectronic receivers, custom monolithic GaAs laser drivers, and an electrical 32×32 silicon crossbar switch. 470 Mb/s operation has been achieved with a bit error rate of less than 10-12. The approach uses a monolithic GaAs optoelectronic integrated receiver to convert optical signals into electr... View full abstract»

The design and characterization of the first integrated optic modulator for a commercial instrument application are described. Alternative forms of modulation, including direct laser current modulation and optical heterodyne techniques, are reviewed for the application, which requires modulation to 20 GHz. The advantages of an integrated optic modulator fabricated using titanium in-diffused lithiu... View full abstract»

A wavelength-selective directional coupler, consisting of two polished single-mode fibers with different cladding refractive indexed, has been fabricated. In contrast to symmetrical couplers, where the power transfer characteristic is a quasiperiodic function of the wavelength, couplers made of dissimilar fibers show a true bandpass-filter characteristic. They consist of two fibers with different ... View full abstract»

Applications of high-resolution optical time domain instrumentation systems for the sensing of strain and temperature using optical fibers are discussed. It is demonstrated that optical fiber segmentation using partially reflective splices allows measurement of localized fiber parameters. In particular, localized fiber strain is measured using specially designed in-line reflectors spaced less than... View full abstract»

An experimental balanced optical phase-locked loop was constructed using two 1320 nm diode-laser pumped miniature Nd:YAG lasers. With a natural frequency of 13.5 kHz and a damping factor of 0.6, the loop phase error is less than 13.° when the received signal power P s is -65 dBm. For signal powers Ps⩾-62 dBm, the phase error is 0.3°, and is virtu... View full abstract»

Two novel tap designs are demonstrated based on phase-matched coupling from the fundamental mode of a fiber to a higher-order core-guided or cladding-guided mode through the acoustooptic effect. The acoustic waves are coupled to the fiber using a Hertzian (deformed surface-to-surface) contact with a grooved transducer substrate. The first tap consists of a two-mode fiber coupler in conjunction wit... View full abstract»

A flip-chip interconnection technique using small solder bumps instead of conventional wire bonding for high-speed broadband photoreceivers is described. The technique achieves interconnection with low parasitic elements, no damage to devices, and easy assembly. A photoreceiver composed of a broadband p-i-n photodiode and a laser-speed GaAS metal-semiconductor field-effect transistor (MESFET) prea... View full abstract»

The high-power characteristics (180 mW, CW) and reliability of 1.48-μm Fabry-Perot laser diodes are studied for V-grooved inner stripe lasers grown by liquid phase epitaxy on p-type substrate (VIPS lasers). Their potential as pumping sources of erbium-doped fiber amplifiers is reported, and their power saturation behavior at several wavelengths is discussed. Aging tests were conducted at high p... View full abstract»

An optical bit-rate flexible transmission system using erbium-doped fiber amplifiers (EDFAs) is proposed, and the system design is discussed. An optical bit-rate flexible system using multiple in-line erbium-doped fiber amplifiers has produced a regenerative repeater spacing of 505 km at 10 Gb/s and 523 km at 5 Gb/s for direct-detection systems. This system proves that an optical bit-rate flexible... View full abstract»

Recent results on silicon bipolar ICs for lightwave communications in the multigigabits-per second (Gb/s) range are presented. These state-of-the-art results demonstrate the inherent speed difference between the different types of basic circuits. With the fastest ones (multiplexing and demultiplexing), bit rates above 10 Gb/s are achieved, even with production technologies. The technologies, as we... View full abstract»

An optical time-domain reflectometer operating at room temperature with the single-photon counting technique is described. It features subcentimeter resolution without data deconvolution, and the capability of observing Rayleigh scattering a few centimeters after a reflecting (Fresnel) discontinuity. The key component for the instrument is a silicon single-photon detector of a new design. Time res... View full abstract»

An equalizer, which is essential in order to improve the sensitivity of receiver optoelectronic integrated circuits (OEICs) at a gigabit-per-second data rate, has been monolithically integrated on an InP substrate with a p-i-n photodiode and a high-impedance high-electron-mobility-transistor (HEMT) amplifier. The receiver operated up to 1.6 Gb/s and showed low noise current characteristics. The mi... View full abstract»

Seeks to establish a high level of confidence in fiber cladding diameter measurement by the use of three methods: white light interferometry, mechanical contact, and image inverting microscopy. Calibration with transfer fibers is considered unattractive because of the difficulty of maintaining the calibrated cleaved end. The uncertainties involved in calibrating other methods are investigated, nam... View full abstract»

The fabrication process and characteristics, including 5-Gb/s transmission, of an integrated light source consisting of a λ/4-shifted distributed feedback laser and an electroabsorption (EA) modulator are discussed. By introducing a semi-insulating (SI) InP on the butt-joint region, both the large electrical isolation resistance (>10 MΩ) between the laser and the modulator and a hi... View full abstract»

A correlation is reported between the intensity of the 630-nm drawing-induced band in undoped silica-core fibers and the abatement of photobleaching by 865-nm light of ionizing radiation-induced loss at 865 nm following gamma-ray exposure at -55°C. At -55°C, undoped silica-core fibers, both low- and high-OH containing, and polymer and glass clad, show intense, 865-nm photostimulated recove... View full abstract»