Showing papers in "IEEE Photonics Technology Letters in 1997"
TL;DR: In this paper, the optically pumped semiconductor (OPS) vertical-external-cavity surface-emitting laser (VECSEL) was demonstrated using diode laser pump.
Abstract: We report demonstration of a new high-power semiconductor laser technology, the optically pumped semiconductor (OPS) vertical-external-cavity surface-emitting laser (VECSEL). Using diode laser pump, an OPS-VECSEL laser with a strain-compensated InGaAs-GaAsP-GaAs multiquantum-well (MQW) structure operated continuous-wave (CW) near /spl lambda//spl sim/1004 nm with record output power of 0.69 W in a TEM/sub 11/ mode, 0.52 W in a TEM/sub 00/ mode, and 0.37 W coupled to a single-mode fiber. It is feasible to produce greater than 1 W of power in a diffraction-limited circular beam from an efficient, compact, manufacturable and reliable OPS-VECSEL laser.
585 citations
TL;DR: In this article, a silica-based erbium doped fiber amplifier (EDFA) with a flat gain bandwidth exceeding 40 nm is described, and the dual-stage EDFA includes a precisely designed inter-stage long-period fiber grating filter with more than 14dB peak attenuation.
Abstract: Broad-bandwidth amplification is essential for the construction of high-capacity multichannel communication systems. We describe a silica-based erbium doped fiber amplifier (EDFA) with a flat gain bandwidth exceeding 40 nm. The dual-stage EDFA includes a precisely designed inter-stage long-period fiber grating filter with more than 14-dB peak attenuation. By careful choice of the filter spectrum and fiber lengths, this EDFA is flat to within 1 dB over 40 nm while producing a noise figure below 4.0 dB and nearly +15-dBm output power.
248 citations
TL;DR: In this paper, the authors presented the first measured data on a Bragg reflection grating based fiber-optic prism true time delay processor for transmit/receive phased array beamforming, which takes maximum advantage of component reuse and fully integrates the transmit and receive modes in one efficient hardware compressive topology.
Abstract: This letter presents, for the first time, measured data on a Bragg reflection grating based fiber-optic prism true time delay processor for transmit/receive phased array beamforming. Measurements taken over a 3.5-GHz bandwidth demonstrates high resolution beamsteering and highly linear low-noise phase data. The system takes maximum advantage of component reuse and fully integrates the transmit and receive modes in one efficient hardware compressive topology.
195 citations
TL;DR: In this article, the first simultaneous measurement of strain and temperature using Brillouin backscatter in an optical fiber was presented, which achieved a 100/spl mu//spl epsiv/ strain and 4/spl deg/C temperature resolution, with 40m spatial resolution, over a sensing length of 1200 m.
Abstract: We report here the first simultaneous measurement of strain and temperature using Brillouin backscatter in an optical fiber. A new sensor arrangement is presented which allows the distributed measurement of Brillouin spectra. Simultaneous measurement of spontaneous Brillouin power and Brillouin shift distributions are made from these spectra, and from this information, we obtain fully distributed measurements of strain and temperature. Our sensor achieves a 100-/spl mu//spl epsiv/ strain and 4/spl deg/C temperature resolution, with 40-m spatial resolution, over a sensing length of 1200 m.
189 citations
TL;DR: In this article, the effects of channel loss on an erbium-doped fiber amplifier (EDFA) in an eight-channel WDM network were investigated, and the authors showed that for the loss of 1, 4, or 7 channels, the surviving channels suffer power transients which can be both large and relatively fast.
Abstract: The effects of channel loss on an erbium-doped fiber amplifier (EDFA) in an eight-channel WDM network are investigated. For the loss of 1, 4, or 7 channels, the surviving channels suffer power transients which can be both large and relatively fast. The experiments agree well with a simple analytical model of the amplifier. Pump control, if it is fast enough, is demonstrated to limit the power excursion of the surviving channels.
183 citations
TL;DR: The phase-shaped binary transmissions (PSBT) as discussed by the authors allow to bridge more than 200 km in the linear regime over standard dispersive fibers, which are based on phase shifts occurring in the middle of some "0" hits inside a binary sequence.
Abstract: This letter presents the phase-shaped binary transmissions (PSBT), which allow to bridge more than 200 km in the linear regime over standard dispersive fibers. These transmissions are based on /spl pi/ phase shifts occurring in the middle of some "0" hits inside a binary sequence. An analytical explanation is given. This letter also explains why 2-intensity level duobinary transmissions, which are a particular case of PSBT, were able to bridge experimentally up to 243 km.
173 citations
TL;DR: In this paper, the authors compared non-return-to-zero (NRZ) and return-tozero (RZ) signal transmission in dispersion-managed high-speed time-division multiplexed (TDM) systems operating at 1.55 /spl mu/m over the already installed standard-fiber network.
Abstract: Nonreturn-to-zero (NRZ) and return-to-zero (RZ) signal transmission in dispersion-managed high-speed time-division multiplexed (TDM) systems operating at 1.55 /spl mu/m over the already installed standard-fiber network are compared by numerical simulations. It is shown that for upgrading the existing network to 40 Gb/s, the RZ-modulation format is superior compared to conventional NRZ-modulation. Standard fiber transmission distances of about 1200 km and 400 km are shown to be feasible within the RZ- and NRZ-format, respectively.
167 citations
TL;DR: In this paper, the authors demonstrate the first phase-array wavelength multiplexer fabricated in the silicon-on-insulator (SOI) waveguide technology, which has a channel spacing of 1.9 nm centered at 1550-nm wavelength and a 3-dB channel bandwidth of 0.72 nm.
Abstract: We demonstrate the first phased-array wavelength multiplexer fabricated in the silicon-on-insulator (SOI) waveguide technology. The four-channel wavelength division multiplexer (WDM) has a channel spacing of 1.9 nm centered at 1550-nm wavelength and a 3-dB channel bandwidth of 0.72 nm. The crosstalk to neighboring channels is less than -22 dB and the on-chip insertion loss is below 6 dB for all channels. The TE-TM shift is less than 0.04 nm which is the smallest attained without compensation techniques in any integrated optic technology.
157 citations
TL;DR: In this article, the authors investigated the operating conditions for modulation bandwidth enhancement, noise reduction, and stable locking to simultaneously fulfill in a semiconductor laser subject to strong optical injection and showed that the optimum detuning of the injection frequency exists as a tradeoff between bandwidth enhancement and noise reduction.
Abstract: Operating conditions for modulation bandwidth enhancement, noise reduction, and stable locking to be simultaneously fulfilled in a semiconductor laser subject to strong optical injection are investigated. When the strength of the injection signal is fixed, the optimum detuning of the injection frequency exists as a tradeoff between bandwidth enhancement and noise reduction. When the laser is injection-locked at a given value of frequency detuning in the stable locking region, both bandwidth enhancement and noise reduction are improved as the injection parameter is increased over a wide range.
148 citations
TL;DR: In this paper, a new method for chromatic-dispersion compensation is proposed and demonstrated, which can produce a chromatic dispersion practically in a wide range from -2000 to +2000 ps/nm and can compensate simultaneously for the dispersion of over 60 wavelength channels with 100 GHz spacing in a WDM system that has a total bandwidth of over 50 nm.
Abstract: A new method for chromatic-dispersion compensation is proposed and demonstrated. This method can produce a chromatic dispersion practically in a wide range from -2000 to +2000 ps/nm and can compensate simultaneously for the dispersion of over 60 wavelength channels with 100-GHz spacing in a wavelength-division multiplexed (WDM) system that has a total bandwidth of over 50 nm. This method has further attractive features such as very small polarization-state dependence, mechanically variable chromatic dispersion, and potential for small packaging. It was experimentally confirmed that this method compensated for the chromatic dispersion accumulated through 110 km standard single-mode fiber (SMF) at 1.55-/spl mu/m wavelength and that 10-Gb/s signal quality was clearly recovered after the 110-km transmission.
148 citations
TL;DR: In this paper, a single-stripe GaAs-AlGaAs optical amplifier was used to generate four tunable wavelength division multiplexed (WDM) channels simultaneously, each transmitting 12-ps pulses at 2.5 GHz, for an aggregate pulse rate of 10 GHz.
Abstract: A single-stripe GaAs-AlGaAs semiconductor optical amplifier (SOA) has been used to generate four tunable wavelength-division multiplexed (WDM) channels simultaneously, each transmitting 12-ps pulses at 2.5 GHz, for an aggregate pulse rate of 10 GHz. Wavelength tuning over 18 nm has been demonstrated with channel spacing ranging from 0.8 to 2.1 nm. A potential spectral correlation across the multiwavelength spectrum has been studied in both experiment and simulation methods. These results show the potential for utilizing single stripe laser diodes as multiwavelength sources in WDM-TDM network.
TL;DR: In this paper, the authors obtained pulsed lasing operation in 2-5/spl mu/m diameter microdisk injection lasers using GaInAsP-InP compressively-strained multiple-quantum-well (MQW) wafers around room temperature.
Abstract: We have obtained pulsed lasing operation in 2-5-/spl mu/m diameter microdisk injection lasers using GaInAsP-InP compressively-strained multiple-quantum-well (MQW) wafers around room temperature. The effective cavity volume of the 2-/spl mu/m-diameter device is the smallest among those for any type of electrically-pumped lasers. The threshold current of this device was as low as 0.2 mA. Cavity modes in emission spectra observed under CW conditions coincide well with theoretically predicted whispering gallery modes. Further reduction of diameter to less than 1.5 /spl mu/m will realize the condition for spontaneous emission almost coupling into a single mode, which results in thresholdless lasing operation.
TL;DR: In this paper, the intrinsic modulation characteristics of an injection-locked semiconductor laser were investigated and the regenerative amplification spectra of a weak optical probe in the laser were derived.
Abstract: Optical probing of an injection-locked semiconductor laser is used to show significant improvement in the intrinsic broad-band modulation characteristics relative to the free-running case. The regenerative amplification spectra of a weak optical probe in the injection-locked laser are in good agreement with the predictions of a conventional coupled-equation model. Based on the regenerative amplification spectra, the intrinsic modulation characteristic due to a weak injection current modulation can be calculated. It shows approximately a factor of three enhancement of the modulation bandwidth, beyond the K-factor limit of the free-running laser.
TL;DR: In this paper, the authors report the successful system demonstration of a four-wavelength integrated-optics amplifying combiner, which consists of an all-connectorized 4/spl times/1 glass splitter followed by a 4.5 cm-long Er/Yb-doped waveguide amplifier.
Abstract: We report the successful system demonstration of a four-wavelength integrated-optics amplifying combiner. The arrangement consists of an all-connectorized 4/spl times/1 glass splitter followed by a 4.5-cm-long Er/Yb-doped waveguide amplifier. When injecting 120 mW of 975-nm laser diode pump, we record, in the amplifying section, 11.6 dB of net gain in the single pass configuration and 23 dB in the double pass as well as a noise figure of 4.5 dB. These results show the potentiality of ion-exchange technology for the fabrication of lossless telecommunication devices.
TL;DR: In this article, a gain-flattened Er/sup 3+/-doped silica-based fiber amplifier (EDFA) was constructed for a 1.58-/spl mu/m band WDM signal.
Abstract: A gain-flattened Er/sup 3+/-doped silica-based fiber amplifier (EDFA) has been constructed for a 1.58-/spl mu/m band WDM signal. This EDFA exhibits uniform amplification characteristics with a gain excursion of 0.9 dB for a four-channel WDM signal in the 1.57-1.60 /spl mu/m wavelength region. The average signal gain and the noise figure for the WDM signal are 29.5 dB and less than 6.3 dB, respectively. The use of this EDFA in parallel with a 1.55-/spl mu/m band EDFA will expand the WDM transmission wavelength region.
TL;DR: In this paper, a quantum cascade distributed-feedback (QCDFB) with a grating close to the active region is reported, where feedback is provided by the grating in a refractive index-dominated coupling scheme.
Abstract: Quantum-cascade distributed-feedback lasers (QCDFB) with a grating close to the active region are reported. Feedback is provided by the grating in a refractive index-dominated coupling scheme. Reliable single-mode emission at /spl lambda//sub cm//spl ap/5.4 /spl mu/m with a side-mode suppression ratio (SMSR) /spl ap/30 dB is observed. The laser is continuously tunable over 40 nm with a coefficient of /spl Delta//spl lambda///spl Delta/T/spl ap/0.37 nm/K in the temperature range from 200 K to 300 K. Comparison with Fabry-Perot QC lasers shows an overall improved performance of QC-DFB lasers.
ETSI1
TL;DR: In this article, a novel approach of true-time delay (TTD) optical feeder for phased-array antennas is proposed and demonstrated by employing tunable lasers and one wide bandwidth chirped-fiber grating as dispersive element.
Abstract: A novel approach of true-time delay (TTD) optical feeder for phased-array antennas is proposed and demonstrated. A compact size continuously variable TTD is achieved by employing tunable lasers and one wide bandwidth chirped-fiber grating as dispersive element. A high-resolution performance (5.3 ps) is obtained for a 26-GHz phased-array antenna employing narrow tuning bandwidth lasers with a wavelength stability of 0.005 nm and a 4 nm bandwidth chirped grating.
TL;DR: In this article, Raman amplification is added to a transmission system to provide an increase in power budget allowing for a four-fold upgrade in capacity either by TDM or WDM.
Abstract: Raman amplification is added to a transmission system to provide an increase in power budget allowing for a four-fold upgrade in capacity either by TDM or WDM. Here, a TDM upgrade from 2.5 to 10 Gb/s and a WDM upgrade from a single 10-Gb/s channel to four channels of 10 Gb/s each were experimentally verified with an improvement in the power budget of 7.4 dB. Raman gain is an attractive upgrade method for installed systems requiring no changes to the fiber span.
TL;DR: In this article, the authors characterized the high-speed modulation properties of thin-oxide-apertured vertical-cavity lasers and showed that the modulation response scales with device diameter due to the negligible optical scattering loss.
Abstract: We characterize the high-speed modulation properties of thin-oxide-apertured vertical-cavity lasers. The modulation response scales with device diameter due to the negligible optical scattering loss present in these devices. A small diameter laser of 3.1 /spl mu/m has a maximum 3-dB bandwidth of 15.2 GHz at a bias of only 2.1 mA. Modeling indicates a no-parasitic bandwidth of 18.2 GHz at this current level, with an intrinsic 3-dB bandwidth limit of 45 GHz due to gain compression. The present devices are limited by parasitic capacitance across the thin oxide layer.
TL;DR: In this paper, a high-speed 1.55/spl mu/m laser diodes with a 3dB modulation bandwidths of 30 GHz were fabricated by using short-cavity mushroom structures with undoped, strain-compensated InGaAlAs-InGaAsP twenty-quantum-well active regions.
Abstract: High-speed 1.55 /spl mu/m laser diodes with a 3-dB modulation bandwidths of 30 GHz were fabricated by using short-cavity mushroom structures with undoped, strain-compensated InGaAlAs-InGaAsP twenty-quantum-well active regions. The bandwidths were achieved at low bias current of 100 mA. The laser exhibited a high differential gain of 1.54/spl times/10/sup -15/ cm/sup 2/ and a small K factor of 0.135 ns. These results were achieved by using an In/sub 0.386/Ga/sub 0.465/AlAs barrier with 0.83% tensile strain to reduce the thermal emission time of holes from wells and hence the hole transport time.
TL;DR: In this article, a phase diversity detection method for compensating for polarization mode dispersion (PMD) in optical fiber at 10 Gb/s is described. But this method relies on a three-sectioned polarization maintaining fiber that provides a controlled amount of PMD in the range of 1.6-42 ps.
Abstract: A phase diversity detection method is described for compensating for polarization mode dispersion (PMD) in optical fiber at 10 Gb/s. The PMD distorted received signal is separated into its two constituent principal states of polarization (PSP) by maximizing the measured phase difference between the two pseudorandom data streams. The PMD is inferred from the measured phase and the two data streams are resynchronized by introducing appropriate delay/advance in their respective paths prior to merging in a combiner. The PMD source is a specially constructed three-sectioned polarization maintaining fiber that provides a controlled amount of PMD in the range of 1.6-42 ps.
TL;DR: In this article, the authors presented novel concepts for tunable optical filters with two-chip designs, and achieved a fine-grasp of 46.7, a fullwidth at half-maximum (FWHM) of 1.2 nm and electrostatic tuning over a range of 103 nm with an applied voltage of 35 V.
Abstract: We present novel concepts for tunable optical filters. Long resonant cavities of about 30-/spl mu/m length have been realized with two-chip designs. GaAs technology has been applied to filters that are designed for the use in dense wavelength-division multiplexing (WDM) at wavelengths around 1550 nm. A finesse of 46.7, a full-width at half-maximum (FWHM) of 1.2 nm and electrostatic tuning over a range of 103 nm with an applied voltage of 35 V has been achieved. An alternative tuning concept that allows to tune the resonator length 4 /spl mu/m by heating Ni-Cr resistors placed on the suspending beams of a membrane with an applied voltage of 2.7 V has been realized.
TL;DR: In this paper, a two-dimensional optical lock-in amplifier with the micro-channel spatial light modulator is developed to detect selectively the coherence component, so that the limitation to the depth resolution introduced by the holographic detection which was used in previous systems is overcome.
Abstract: A novel optical information processing system by synthesis of the coherence function is built up to extract a two dimensional image from a three-dimensional object at a tenable depth with neither mechanical scanning nor digital calculation. In this system, a two-dimensional optical lock-in amplifier with the microchannel spatial light modulator is developed to detect selectively the coherence component, so that the limitation to the depth resolution introduced by the holographic detection which was used in our previous systems is overcome. Selective image extraction Is demonstrated successfully.
TL;DR: In this article, a link control technique for protecting surviving channels on a per-link basis from fast power transients resulting from network reconfigurations or line failures is demonstrated in a 560-km eight-amplifier wavelength division multiplexed link carrying seven 2.5-Gb/s channels plus the link control channel.
Abstract: Link control, a new technique for protecting surviving channels on a per-link basis from fast power transients resulting from network reconfigurations or line failures, is demonstrated in a 560-km eight-amplifier wavelength division multiplexed link carrying seven 2.5-Gb/s channels plus the link control channel.
TL;DR: In this paper, the room-temperature pulsed operation of a semiconductor laser emitting at 8.5 /spl mu/m was reported, and the peak output power from a single facet was 15 mW, and current density at threshold was /spl sim/8 kA/cm/sup 2.
Abstract: The room-temperature pulsed operation of a semiconductor laser emitting at 8.5 /spl mu/m is reported. This device is an optimized vertical transition quantum cascade (QC) laser. At 300 K the peak output power from a single facet is 15 mW, and the current density at threshold is /spl sim/8 kA/cm/sup 2/. The temperature dependence of the threshold current density is described by a high T/sub 0/ (107 K) in the 200-320 K temperature range.
ETSI1
TL;DR: In this article, the amplitude of the electric field of a lightwave propagating through a fiber Bragg grating was calculated based on a transfer matrix method developed for electric field calculations in multilayer thin films.
Abstract: We have developed a technique to calculate the amplitude of the electric field of a lightwave propagating through a fiber Bragg grating (FBG). The technique is based on a transfer matrix method developed for electric field calculations in multilayer thin films. The internal electric field distribution of FBG structures having uniform, tapered chirped, and phase-shifted index modulations has been calculated. Two-dimensional plots of the average internal power versus the distance along the grating axis and light frequency are presented.
TL;DR: In this paper, a high extinction ratio wavelength conversion was demonstrated in a semiconductor optical amplifier using a mixture of cross-gain and cross-phase modulation in a polarization rotation technique.
Abstract: High-extinction-ratio wavelength conversion has been demonstrated in a semiconductor optical amplifier using a mixture of cross-gain and cross-phase modulation in a polarization rotation technique. 40-ps-wide pulses at 1311 nm have been generated using 47-ps, 5.7-mW peak-power input pulses at 1300 nm. Excellent agreement with experiment has been obtained using a computer model.
TL;DR: In this article, a simplified analysis of noise in concatenated nonlinear analog optoelectronic repeaters is conducted, and it is shown that the bit error rate (BER) accumulation can be reduced significantly compared to a linear scheme, even with a partial nonlinearity.
Abstract: A simplified analysis of noise in concatenated nonlinear analog optoelectronic repeaters is conducted. We investigate different shapes of the nonlinearity and show that the bit-error-rate (BER) accumulation can be reduced significantly compared to a linear scheme, even with a partial nonlinearity. The results are also compared with a corresponding optically amplified linear system at 10 Gb/s.
TL;DR: In this paper, a cascade of two directional couplers with a relative phase shift between them, serves as an optical power divider, and simple analytic universal design rules for selecting the appropriate net coupling strength in each device, and for the phase shift, yield maximally flat response in terms of deviations in wavelength, polarization, or uniform fabrication errors, and are applicable to any power division ratio.
Abstract: A cascade of two directional couplers with a relative phase shift between them, serves as an optical power divider. Simple analytic universal design rules for selecting the appropriate net coupling strength in each device, and for the phase shift, yield maximally flat response in terms of deviations in wavelength, polarization, or uniform fabrication errors, and are applicable to any power division ratio.
TL;DR: In this paper, the effect of birefringence on the selection of polarization states of a weakly index guided vertical-cavity surface-emitting laser (VCSEL) supporting both a fundamental and a first-order transverse mode was investigated.
Abstract: An analysis has been undertaken of the effect of birefringence on the selection of polarization states of a weakly index guided vertical-cavity surface-emitting laser (VCSEL) supporting both a fundamental and a first-order transverse mode. It is shown that for small index steps polarization switching due to spatial-hole burning effects can occur. For larger index steps it is found that higher order modes can emerge which are orthogonally polarized to the dominant polarization of the fundamental mode.