Showing papers in "IEEE Photonics Technology Letters in 1992"
TL;DR: In this article, a fast, automated system using a tunable laser and an accurate, real-time polarimeter affords the temporal accuracy of approximately 2% down to a limit of several femtoseconds, as demonstrated by comparison with other techniques and comparison with known samples.
Abstract: Polarization mode dispersion (PMD), which can limit the bandwidth of optical transmission links, has been difficult to measure in a manner independent of human judgment, leading to difficulties in automating the measurement. It is shown that PMD in any linear, time-invariant network can be completely characterized by eigenanalysis of Jones matrices measured at a series of discrete wavelengths, even for networks exhibiting polarization-dependent loss. A fast, automated system using a tunable laser and an accurate, real-time polarimeter affords the temporal accuracy of approximately 2% down to a limit of several femtoseconds, as demonstrated by comparison with other techniques and comparison with known samples. Both the principal states of polarization and the group delay difference were measured as a function of optical frequency. >
351 citations
TL;DR: In this article, a passive and self-referencing wavelength detection system that measures the wavelength of the narrowband back-reflected spectrum of guided-wave Bragg gratings is described.
Abstract: A novel, passive, and self-referencing wavelength detection system (WDS) that measures the wavelength of the narrowband back-reflected spectrum of guided-wave Bragg gratings is described. This letter also reports on the use of such a detection system with fiber-optic Bragg gratings used as absolute strain sensors. The wavelength detection system demonstrated a 1% strain resolution of the total strain measurement range. >
333 citations
TL;DR: In this article, the authors used the wavelength region around the zero-dispersion wavelength of an optical fiber to convert 622 Mbt/s FSK signal light from 1555.2 to 1547.6 nm with a conversion efficiency of -24 dB.
Abstract: Wavelength conversion using fiber four-wave mixing in an optical fiber is demonstrated. Utilizing the wavelength region around the zero-dispersion wavelength of a fiber, 622 Mbt/s FSK signal light is converted from 1555.2 to 1547.6 nm with a conversion efficiency of -24 dB. >
246 citations
TL;DR: In this article, a wideband heterodyne second-order optical phase-locked loop with 1.5-mu m semiconductor lasers is presented, which has a bandwidth of 180 MHz, gain of 181 dBHz, and a propagation delay of only 400 ps.
Abstract: Experimental results of a wideband heterodyne second-order optical phase-locked loop with 1.5- mu m semiconductor lasers are presented. The loop has a bandwidth of 180 MHz, a gain of 181 dBHz, and a propagation delay of only 400 ps. A beat signal of 8 MHz linewidth is phase locked to become a replica of a microwave reference source close to carrier with a noise level of -125 dBc/Hz. The total phase variance of the locked carrier is 0.04 rad/sup 2/ and carriers can be generated in a continuous range from 3 to 18 GHz. The loop reliability is excellent with an average time to cycle slip of 10/sup 11/ s and an acquisition range of 640 MHz. >
237 citations
TL;DR: In this paper, it was shown that attenuating the reference power in an optical low-coherence reflectometry (OLCR) measurement, the reflection sensitivity can be improved, even though, in many other types of optical measurements, sensitivity is improved as optical power is increased.
Abstract: It is shown that by attenuating the reference power in an optical low-coherence reflectometry (OLCR) measurement, the reflection sensitivity can be improved, even though, in many other types of optical measurements, sensitivity is improved as optical power is increased. The difference is due to the presence of inherent intensity noise associated with low-coherence sources, which can dominate over shot noise at optical powers that are as low as 1 mu W. A reflection sensitivity of -146 dB is demonstrated using this technique. >
225 citations
TL;DR: In this article, the authors introduce simple techniques to solve gain equalization problems in amplified wavelength-multiplexed lightwave transmission systems by adjusting the channel powers at the terminals in a prescribed way.
Abstract: The authors introduce simple techniques to solve gain equalization problems in amplified wavelength-multiplexed lightwave transmission systems. By adjusting the channel powers at the terminals in a prescribed way, either the output powers or the output signal-to-noise ratios of all the channels can be equalized. All adjustments can be made using information provided by system telemetry. No new equipment, upgrades, or adjustments are required at intermediate amplifier sites. >
208 citations
TL;DR: Using high-resolution optical reflectometry, group index and physical thickness can both be determined by precisely measuring optical time delays through a sample as mentioned in this paper, which offers both the high-spatial resolution and large dynamic range required to perform accurate measurements using this technique.
Abstract: Using high-resolution optical reflectometry, group index and physical thickness can both be determined by precisely measuring optical time delays through a sample. Optical low-coherence reflectometry offers both the high-spatial resolution and large dynamic range required to perform accurate measurements using this technique. >
203 citations
TL;DR: In this paper, the modulation bandwidth of quantum well lasers can be reduced by a factor of six due to carrier transport across undoped layers of the laser as in the separate confinement heterostructure (SCH).
Abstract: It is shown experimentally that the modulation bandwidth of quantum well lasers can be reduced by a factor of six due to carrier transport across undoped layers of the laser as in the separate confinement heterostructure (SCH). Analytical expressions are given for the modulation response function, resonance frequency, damping rate and K factor to include carrier transport, and it is shown that carrier transport is responsible for a low-frequency rolloff which limits the modulation response of quantum-well lasers. It also shown that carrier transport leads to a reduction in the effective differential gain, while the gain compression factor remains largely unaffected by it. >
162 citations
TL;DR: In this article, a minimum reflection sensitivity of -148 dB was reported for optical low-coherence reflectometry using optical singlemode fiber with a spatial resolution of 32 mu m and a dynamic range of over 30 dB.
Abstract: Rayleigh backscattering at a wavelength of 1.55 mu m is measured in standard single-mode fiber with a spatial resolution of 32 mu m and a dynamic range of over 30 dB. A minimum reflection sensitivity of -148 dB is the best reported to date using optical low-coherence reflectometry. >
151 citations
TL;DR: The traveling-wave photodetector (TWPD) as mentioned in this paper is an edge-coupled photoder that is capable of both a larger absolute bandwidth and a larger bandwidth-efficiency product than the WGPD.
Abstract: The authors propose and analyze the traveling-wave photodetector (TWPD), an edge-coupled photodetector that is capable of both a larger absolute bandwidth and a larger bandwidth-efficiency product than the waveguide photodetector (WGPD). The intrinsic RC bandwidth limitation is increased in the traveling-wave photodetector by providing for controlled transmission of the electrical wave down the device in parallel with the optical wave and by eliminating bandwidth-limiting electrical reflections. It is shown that 1- mu m wide, parallel-plate, GaAs/AlGaAs, p-i-n TWPD with open-circuit input termination has a 26% greater potential bandwidth-efficiency product than the comparable WGPD, while a TWPD with matched input termination actually has a worse bandwidth-efficiency product than the WGPD. >
142 citations
TL;DR: In this paper, a temperature sensor based on fiber-optic Bragg grating elements is described, and a high sensitivity to thermally induced Bragg wavelength shifts is obtained using an interferometric detection approach.
Abstract: A differential temperature sensor based on fiber-optic Bragg-grating elements is described. A high sensitivity to thermally induced Bragg wavelength shifts is obtained using an interferometric detection approach. Results presented show a temperature resolution of >
TL;DR: In this paper, two star couplers with a waveguide grating were used to construct a monolithic 15*15 multiplexer with a free spectral range of 10.5 nm (1.3 THz) and channel spacing of 0.7 nm (87 GHz) at 1550 nm wavelength.
Abstract: By interconnecting two star couplers with a waveguide grating, the authors built a monolithic 15*15 multiplexer on InP. The grating order of 148 gives a free spectral range of 10.5 nm (1.3 THz) and a channel spacing of 0.7 nm (87 GHz) at 1550 nm wavelength. A crosstalk between adjacent channels of less than 18 dB and a residual crosstalk of less than 25 dB were obtained. The on-chip insertion loss is typically 2-4 dB. >
TL;DR: In this paper, a high-resolution optical frequency-domain reflectometer (OFDR) which employs the frequency sampling method is reported, and the auxiliary interferometer for generating the clock pulses at equally spaced light frequencies is incorporated into the main interferometers to simplify the system configuration and to reduce the effect of different environmental perturbations occurring at the two interferriers.
Abstract: A high-resolution optical frequency-domain reflectometer (OFDR) which employs the frequency sampling method is reported. The auxiliary interferometer for generating the clock pulses at equally spaced light frequencies is incorporated into the main interferometer to simplify the system configuration and to reduce the effect of different environmental perturbations occurring at the two interferometers. 180-MHz frequency sampling is shown to give an 850- mu m spatial resolution and -80-dB minimum detectable reflectivity through the use of a DFB-LD with 180-GHz nonlinear chirp. >
TL;DR: In this paper, a singlemode As/sub 2/S/sub 3-based glass fiber was used for ultrafast all-optical switching with a switching power of 14 W.
Abstract: Ultrafast all-optical switching with a switching power of 14 W was demonstrated in a Kerr shutter configuration using a single-mode As/sub 2/S/sub 3/-based glass fiber only 48 cm long. The nonlinear refractive index of the fiber was evaluated from the switching characteristics to be n/sub 2/=4.2*10/sup -14/ (cm/sup 2//W), which is higher by two orders of magnitude than silica glass fiber. >
TL;DR: In this paper, the design and experimental results for a temporal/spatial (T/S) noncoherent optical code-division multiple access (CDMA) based on matrix codes, using a breadboard of passive multimode fiber-optic couplers and delay lines, are presented.
Abstract: The design and experimental results for a temporal/spatial (T/S) noncoherent optical code-division multiple access (CDMA), based on matrix codes, using a breadboard of passive multimode fiber-optic couplers and delay lines, is presented. It is shown that a T/S CDMA network allows for shorter bit times, given a set laser pulse width, compared to a temporal CDMA network. Also, T/S codes result in a reduction of autocorrelation sidelobes and cross-correlation peaks, and the T/S network has lower losses. It is also shown that the couplers are critical components in maintaining code integrity. >
TL;DR: In this article, it was shown that the global variation of the transmission through any linear, time-invariant optical device, over all states of polarization, can be found in a strictly deterministic, analytically complete manner by measuring the polarization responses to only three input polarizations.
Abstract: Polarization dependence of the loss or gain of an optical device has been difficult to measure in a consistent and reproducible manner because it has been necessary to search for the extrema of transmission over a two-dimensional polarization space. It is shown that the global variation of the transmission through any linear, time-invariant optical device, over all states of polarization, can be found in a strictly deterministic, analytically complete manner by measuring the polarization responses to only three input polarizations. A series of fast, automated measurements of two test devices yielded standard deviations of 0.017 and 0.033 dB and agreement with manual measurements. >
TL;DR: In this article, a grating spectrograph integrated monolithically for the first time in the InGaAsP system with a photodiode array for a dense WDM application is presented for the 1.5 mu m wavelength region.
Abstract: A grating spectrograph integrated monolithically for the first time in the InGaAsP system with a photodiode array for a dense WDM application is presented for the 1.5 mu m wavelength region. The chip provides 42 wavelength channels with a spacing of 4 mm, a channel crosstalk of approximately -15 dB, an internal photodiode efficiency of 90%, and a photodiode capacitance of 0.33 pF. The chip needs no optical adjustments. It is therefore well suited for mass production. >
TL;DR: In this paper, the authors proposed a tunable laser with a striped thin-film heater, which can be continuously tuned over a range of 4 nm while maintaining an optical power of 20 mW and with a linewidth of less than 2.5 MHz.
Abstract: The authors propose a very simple tunable laser with a striped thin-film heater. The wavelength of this laser changes with a sensitivity of 3.2 nm/W to the input heating power. This laser can be continuously tuned over a range of 4 nm while maintaining an optical power of 20 mW and with a linewidth of less than 2.5 MHz. When this laser is mounted on a module, its 90% response time is 6 ms, which is fast enough for use as a local oscillator in several applications. >
TL;DR: In this paper, a reflection spectroscopy technique was used to determine the refractive index of (Al,Ga,In)As films as a function of wavelength, which can be used in the design of waveguides, modulators, and other optical devices.
Abstract: Molecular beam epitaxy (MBE)-grown bulk and short-period superlattices of (Al,Ga,In)As epilayers lattice matched to InP were characterized by double-crystal diffractometry and low-temperature photoluminescence. A reflection spectroscopy technique was used to determine the refractive index of (Al,Ga,In)As films as a function of wavelength. The measured data were fitted to a single-oscillator dispersion model, and the model coefficients are given. The resulting expression can be used in the design of waveguides, modulators, and other optical devices. >
TL;DR: In this paper, a new technique for extracting the intrinsic laser-diode dynamic properties accurately is described, which eliminates the need for accurate microwave calibration of the test equipment and problems of microwave reflections, nonideal frequency response of laser mount, and detector.
Abstract: The authors describe a new technique for extracting the intrinsic laser-diode dynamic properties accurately. This simple technique eliminates the need for accurate microwave calibration of the test equipment and problems of microwave reflections, nonideal frequency response of laser mount, and detector. The effect of the parasitic components of the laser diode are also eliminated from the results so that measurements of important dynamic properties of the laser can be found up to high frequencies (10-20 GHz) on standard laser diodes. The techinque being used to measure variations of resonance peak and damping factor at different bias levels for a standard bulk active region 1.3 mu m laser diode is shown. >
TL;DR: In this paper, a reduction in fading noise which causes amplitude fluctuation on a backscattered trace in coherent OTDR (optical time-domain reflectometry) is described, where the optical frequency of the DFB-LD (distributed feedback laser diode) is changed by changing the LD temperature during the integrations of the back scattered signals.
Abstract: The authors describe a reduction in fading noise which causes amplitude fluctuation on a backscattered trace in coherent OTDR (optical time-domain reflectometry). In order to reduce the fading noise, the optical frequency of the DFB-LD (distributed feedback laser diode) is changed by changing the LD temperature during the integrations of the backscattered signals. At the same time, the state of polarization of the launched signal pulses is changed. The amplitude fluctuation has been reduced to as low as 0.06 dB. Measurements were performed on a 10 km length of conventional single-mode fiber. >
TL;DR: In this article, it was shown that for practical pump powers (33 dB) and low noise figure (3 dB) cannot simultaneously be achieved with a conventional codirectionally pumped EDFA.
Abstract: It is shown that for practical pump powers ( 33 dB) and low noise figure (3 dB) cannot simultaneously be achieved with a conventional codirectionally pumped EDFA. However, using a codirectionally pumped composite EDFA incorporating an isolator overcomes the problem, and an amplifier with 51 dB (54 dB) gain and 3.1 dB noise figure (NF) for only 45 mW (93 mW) of pump power is demonstrated. >
TL;DR: In this paper, a back-illuminated In/sub 0.48/As/InP metal-semiconductor-metal (MSM) detector is reported with a record responsivity of 0.96 A/W at 1.3-mu m wavelength, corresponding to a quantum efficiency of 92%.
Abstract: A high-performance back-illuminated In/sub 0.53/Ga/sub 0.47/As/In/sub 0.52/Al/sub 0.48/As/InP metal-semiconductor-metal (MSM) detector is reported. A record responsivity of 0.96 A/W at 1.3- mu m wavelength, corresponding to a quantum efficiency of 92%, was measured at 5 V and showed virtually no internal gain at 20 V. Packaged devices with 150- mu m-diameter large detection area showed a 3-dB bandwidth of 4 GHz at 5 V with fiber pigtail butt-coupled package and 3.5 GHz with fiber pigtail silicon V-grooved package. Switching to front-illumination improves the bandwidth by 30-40% with 45-50% reduction of responsivity. Planar and mesa devices both show a low capacitance per unit area of 3.0 nF/cm/sup 2/ and dark current density of 5.6*10/sup -5/ A/cm/sup 2/ at 5 V. Preliminary reliability test results show that the detector biased at 5 V survived temperature cycling of -35 degrees C to 200 degrees C, high-temperature burn-in at 125 degrees C for 168 h and subsequent short-term accelerated aging at 200 degrees C for 120 h without degradation. >
TL;DR: In this article, the effects of fiber uniformity on stimulated Brillouin scattering thresholds have been measured and extended to the case of non-uniform fibers, which enables the design of long fiber spans with ten times higher stimulated-branching thresholds.
Abstract: The effects of fiber uniformity on stimulated Brillouin scattering thresholds have been measured, and the theory for stimulated Brillouin scattering in uniform fibers has been extended to the case of nonuniform fibers. This theory enables the, design of long fiber spans with ten times higher stimulated Brillouin scattering thresholds. >
TL;DR: In this article, Carrier heating and spectral hole burning are shown to have a strong influence on the amplification of ultrashort pulses using semiconductor laser amplifiers, and approximate analytical expressions for the effective saturation energy in different pulsewidth regimes are derived.
Abstract: Carrier heating and spectral hole burning are shown to have a strong influence on the amplification of ultrashort pulses using semiconductor laser amplifiers. Approximate analytical expressions for the effective saturation energy in different pulsewidth regimes are derived. >
TL;DR: In this paper, the effect of the thickness of the buried oxide layer on propagation loss has been studied, and the lowest loss was observed for a buried oxide thickness of 0.4 mu m, at a measurement wavelength of 1.523 mu m.
Abstract: Planar optical waveguides have been formed in SIMOX structures, and the effect of the thickness of the buried oxide layer on propagation loss hs been studied. Waveguides with a guiding layer thickness of approximately 6 mu m have been measured, and the lowest loss, which is on the order of that of pure silicon, was observed for a buried oxide thickness of 0.4 mu m, at a measurement wavelength of 1.523 mu m. >
TL;DR: In this article, a fast polarization control system using a lithium niobate electrooptic polarization transformer and a simple electronic feedback circuit is reported. But the system produces general elliptical phase retardation at a maximum rate of 6300 rad/s and allows continuous transformations from any general varying input polarization into any desired output state.
Abstract: A fast polarization control system using a lithium niobate electrooptic polarization transformer and a simple electronic feedback circuit is reported. The system produces general elliptical phase retardation at a maximum rate of 6300 rad/s and allows continuous transformations from any general varying input polarization into any desired output state. The automatic stabilization of a rapidly varying polarization state at rates of up to 4900 rad/s was achieved. >
TL;DR: A dynamic control mechanism, based on subcarrier-multiplexed pilot-tones and acoustooptic tunable filters, is proposed for wavelength routing in a high-capacity wavelength division multiplexed (WDM) SONET interoffice ring network.
Abstract: A dynamic control mechanism, based on subcarrier-multiplexed pilot-tones and acoustooptic tunable filters, is proposed for wavelength routing in a high-capacity wavelength division multiplexed (WDM) SONET interoffice ring network. The authors experimentally verified the network concept and discussed different network applications for bursty data traffic and continuous voice/video traffic. >
TL;DR: In this article, the first ion-exchanged waveguide was demonstrated in a single transverse mode at the lasing wavelength of 1540 nm in a BK-7 glass with 0.5 wt.% erbium-doped glass and pump power thresholds of 150 mW and slope efficiencies of 0.55%.
Abstract: Ion-exchange in glass is a simple, flexible technique to realize optical fiber-compatible planar waveguide devices. Recently, neodymium-doped waveguide lasers operating at 1060 and 1300 nm have been demonstrated in this technology. Lasers operating at 1540 nm are desirable for telecommunication applications and the authors report for the first time ion-exchanged waveguide lasers in erbium-doped glass emitting at this wavelength. Lasers in BK-7 glass doped with 0.5 wt.% Er/sub 2/O/sub 3/ and pumped at 980 nm exhibited launched pump power thresholds of 150 mW and slope efficiencies of 0.55%. The waveguides operated in a single transverse mode at the lasing wavelength. >
TL;DR: In this article, the authors present a general analysis of optical switching fabrics using SOAs, considering noise and saturation effects associated with amplified spontaneous emission, and find that the SOA saturation output power limits the number of switches which can be cascaded.
Abstract: Multiple space-division switches based on semiconductor optical amplifiers (SOAs) can be cascaded to obtain larger switching fabrics. The authors present a general analysis of optical switching fabrics using SOAs, considering noise and saturation effects associated with amplified spontaneous emission. They find that the SOA saturation output power limits the number of switches which can be cascaded. For example, a saturation output power of 100 mW limits the size of switching fabrics to 100 64*64 switches or 200 8*8 switches if distributed gain matrix-vector multiplier (MVM) switches or Benes switches are employed. The corresponding limit for lumped gain MVM fabrics is 10 64*64 or 100 8*8. The Benes switch may be more suitable for large switch size (N>16) because it requires fewer SOAs. >