Showing papers in "IEEE Photonics Technology Letters in 1993"
TL;DR: In this article, an optical nonlinear element asymmetrically placed in a short fiber loop is used for demultiplexing Tb/s pulse trains that requires less than 1 pJ of switching energy and can be integrated on a chip.
Abstract: A device capable of demultiplexing Tb/s pulse trains that requires less than 1 pJ of switching energy and can be integrated on a chip is presented. The device consists of an optical nonlinear element asymmetrically placed in a short fiber loop. Its switching time is determined by the off-center position of the nonlinear element within the loop, and therefore it can use the strong, slow optical nonlinearities found in semiconductors, which all other fast demultiplexers seek to avoid. The switch's operation at 50 Gb/s is demonstrated, using 600-fJ control pulses. >
676Â citations
TL;DR: In this paper, the authors estimate the SNR at the receiver's decision circuit when the bit error ratio (BER) is too low to be measured in a reasonable time, and obtain good agreement between the BER predicted using the measured SNR value and the actual measured BER.
Abstract: The margin, or the difference between the received signal-to-noise (SNR) and the SNR required to maintain a given bit error ratio (BER), is important to the design and operation of optical amplifier transmission systems A new tehnique is described for estimating the SNR at the receiver's decision circuit when the BER is too low to be measured in a reasonable time. The SNR is determined from the behavior of the BER as a function of the decision threshold setting in the region where the BER is measurable. The authors obtain good agreement between the BER predicted using the measured SNR value and the actual measured BER. >
594Â citations
TL;DR: In this article, a potentially inexpensive light source for multichannel WDM applications is proposed, where the high-power amplified spontaneous emission (ASE) from an erbium-doped fiber amplifier (EDFA), which is already in the singlemode fiber, can be efficiently divided into many channels by using an integrated optic wavelength division multiplexing (WDM) demultiplexer.
Abstract: A potentially inexpensive light source for multichannel WDM applications is proposed The high-power amplified spontaneous emission (ASE) from an erbium-doped fiber amplifier (EDFA), which is already in the single-mode fiber, can be efficiently divided into many channels by using an integrated optic wavelength-division-multiplexing (WDM) demultiplexer This spectrum-sliced ASE can be used as light sources for WDM systems in place of several wavelength-selected DFB lasers To demonstrate the principle, the 40-nm-wide ASE spectrum of an EDFA was sliced using a narrow optical filter (3-dB bandwidth: 13 nm), and the resulting source was used for the transmission of up to 17 Gb/s of data The problem of spontaneous-spontaneous beat noise in these sources is dealt with It is estimated that the total capacity would be about 40 Gb/s, realistically, since the channel spacing should be at least three times the optical bandwidth of each channel to avoid crosstalk >
271Â citations
CNET1
TL;DR: In this article, it was shown that in low-concentration erbium-doped silicate fibers (below 1000 p.p.m.), a residual absorption at 980 nm cannot be saturated.
Abstract: It is shown that in low-concentration erbium-doped silicate fibers (below 1000 p.p.m.), a residual absorption at 980 nm cannot be saturated. Usual models for upconversion of Er/sup 3+/ cannot match this behavior nor explain a fluorescence lifetime independent of pump power and erbium concentration. A phenomenon, the pair induced quenching (PIQ), that is compatible with the previous experimental results is exhibited. The influence of erbium and aluminum concentration on the ion pair proportion is shown. >
240Â citations
TL;DR: In this paper, the effective compensation of waveform distortion due to chromatic dispersion in a singlemode fiber was demonstrated using an optical phase-conjugate wave generated by nondegenerate forward four-wave mixing in a zero-dispersion single-mode fiber.
Abstract: The effective compensation of waveform distortion due to chromatic dispersion in a single-mode fiber was demonstrated using an optical phase-conjugate wave generated by nondegenerate forward four-wave mixing in a zero-dispersion single-mode fiber. After transmission of 5- and 6-Gb/s continuous-phase FSK (CPFSK) signal through a dispersive single-mode fiber, distortion compensation was confirmed by measuring bit error rate characteristics and observing heterodyne-detected eye-patterns. >
211Â citations
TL;DR: A optical code-division multiple access (CDMA) system based on amplitude spectral encoding of low-cost broadband sources such as light-emitting diodes is presented and it is shown that by assigning to N subscribers the N cycles shifts of a single unipolar m-sequence of period N, complete orthogonality between the users can be achieved.
Abstract: A optical code-division multiple access (CDMA) system based on amplitude spectral encoding of low-cost broadband sources such as light-emitting diodes is presented. The proposed system uses a standard nondispersive lens-grating apparatus and simple direct-detection receivers. It is shown that by assigning to N subscribers the N cycles shifts of a single unipolar m-sequence of period N, complete orthogonality between the users can be achieved, provided that the spectrum is properly equalized. It is also shown that without any equalization, and for N=511, up to 200 users can transmit asynchronously with an average error probability equal to 10/sup -9/, depending on the received power level. An aggregate network throughput of 100 Gb/s can therefore be obtained. >
206Â citations
TL;DR: In this paper, a microwave signal is transmitted on a wavelength-tunable optical carrier through a fiber-optic prism-a set of equal-delay fibers with differing net dispersion-to photodetectors that feed each antenna element.
Abstract: Experimental results for an optical-control technique for implementing a true time-delay function for array antennas are reported. A microwave signal is transmitted on a wavelength-tunable optical carrier through a fiber-optic prism-a set of nominally equal-delay fibers with differing net dispersion-to photodetectors that feed each antenna element. The relative interelement time-delay (beam angle) adjustment is accomplished by tuning the optical carrier wavelength. Measured antenna patterns of a two-element array clearly demonstrate beam steering and true time-delay operation over a two-octave bandwidth of 2-8 GHz. >
186Â citations
TL;DR: In this article, a spatial filtering concept for the control of VCSEL transverse modes that allows over 1.5mW single TEM/sub 00/ transverse mode emission was introduced.
Abstract: Transverse mode characteristics and control for vertical-cavity top-surface-emitting lasers (VCSELs) are discussed. A spatial filtering concept for the control of VCSEL transverse modes that allows over 1.5-mW single TEM/sub 00/ transverse mode emission to be routinely achieved from continuous-wave electrically excited VCSELs is introduced. Without spatial filtering, L-I and V-I kinks are observed. >
176Â citations
TL;DR: In this paper, a tunable erbium doped fiber laser which utilizes a broadband mirror and an intracore Bragg grating reflector in side-pump configuration is described.
Abstract: The development of a fiber laser sensor system which permits efficient interrogation of Bragg grating sensors is reported. A tunable erbium doped fiber laser which utilizes a broadband mirror and an intracore Bragg grating reflector in side-pump configuration is described. The wavelength of the laser oscillation is determined by the Bragg grating, which is remotely located and used as a strain sensor. This arrangement is used in conjunction with a passive wavelength demodulation system (WDS) to form a self-contained fiber laser strain sensor system, allowing efficient interrogation of the Bragg sensor. This device provides interrupt-immune sensing of static and dynamic strains with a bandwidth of 13.0 kHz. >
170Â citations
TL;DR: Laterally tapered gain regions designed to accommodate the diffraction of narrow single-lobe beams that have been used in both optical amplifiers and lasers are described in this paper, where the authors achieve output power of 3.5 W with 3.1 W in a 1.05 times diffraction-limited lobe.
Abstract: Laterally tapered gain regions designed to accommodate the diffraction of narrow single-lobe beams that have been used in both optical amplifiers and lasers are described. Amplifier output power of 3.5 W with 3.1 W in a 1.05 times diffraction-limited lobe and laser output power of over 4 W with approximately half the power in a 1.7 times diffraction-limited lobe have been achieved. >
164Â citations
TL;DR: In this article, a Mach-Zehnder modulator at an optical bias below the conventional 50% (quadrature) bias was investigated and the theoretical distortion curves as a function of bias were calculated and experimentally verified.
Abstract: Operating a Mach-Zehnder modulator at an optical bias below the conventional 50% (quadrature) bias is investigated. Theoretical distortion curves as a function of bias have been calculated and experimentally verified. These curves show that (single octave) linear dynamic range increases as the bias is lowered, so long as optical power at the detector can be maintained just below the saturation level or laser noise limit. This method thus provides a way for very large optical power to be used to benefit linear dynamic range. Theoretically, 20 dB of excess optical power, attenuated through low biasing, can result in an increase in linear dynamic range of 15 dB. >
TL;DR: In this paper, a polarization-independent frequency conversion over a 1-THz range by fiber four-wave mixing is demonstrated using a polarization diversity technique, where the power of the converted light varies less than 0.2 dB.
Abstract: Polarization-independent frequency conversion over a 1-THz range by fiber four-wave mixing is demonstrated using a polarization diversity technique. The power of the converted light varies less than 0.2 dB. Bit-error-rate (BER) performance of frequency-shift-keying (FSK) direct detection at 622 Mb/s confirms the feasibility of the technique. >
TL;DR: In this article, a sinusoidally driven phase modulator and an optical amplifier are placed within an optical fiber loop, so that the modulation is enhanced by multiple passes through the loop.
Abstract: A method to generate a comb of precisely spaced optical frequencies over a terahertz span is presented. This scheme uses a sinusoidally driven phase modulator and an optical amplifier placed within an optical fiber loop, so that the modulation is enhanced by multiple passes through the loop. By maintaining the loop round-trip gain slightly below unity, a comb of tens to hundreds of frequencies can be generated. If the loop input is derived from a laser locked to an absolute frequency reference, then each of the output frequencies has an absolute accuracy approaching that of the input. >
TL;DR: In this article, a specific fiber dispersion management is proposed allowing the simultaneous suppression of linear dispersion penalties and of degradations arising from parametrical fiber nonlinearities, and the number of optical channels that can be transmitted over 1000 km at a bit rate of 2.5 Gb/s is only limited by the available optical amplifier bandwidth.
Abstract: A specific fiber dispersion management is proposed allowing the simultaneous suppression of linear dispersion penalties and of degradations arising from parametrical fiber nonlinearities. For the proposed dual dispersion configuration (DDCON) the number of optical channels that can be transmitted over 1000 km at a bit rate of 2.5 Gb/s is only limited by the available optical amplifier bandwidth. >
TL;DR: In this paper, the integrated operation of a 16*1 WDM source with distributed Bragg reflector (DBR) lasers and electroabsorption modulators has been demonstrated by using repeated holographic exposures and wet chemical etching, 16 different wavelengths from 1.544 to 1.553 mu m with an average channel spacing of 6 AA.
Abstract: The integrated operation of a 16*1 wavelength-division-multiplexed (WDM) source with distributed Bragg reflector (DBR) lasers and electroabsorption modulators has been demonstrated. By using repeated holographic exposures and wet chemical etching, 16 different wavelengths from 1.544 to 1.553 mu m with an average channel spacing of 6 AA are obtained. A high-performance combiner is used to obtain a very uniform coupling into the single-output waveguide, and with the integration of an optical amplifier an average optical power of -8 dBm per channel is coupled into a single-mode fiber. >
TL;DR: In this paper, a mode-locked pulse source with extremely wide operating frequency range and very stable operation, through the use of a long, linearly chirped Bragg reflector as the output coupler integrated in a fiber external cavity.
Abstract: The authors report a mode-locked pulse source with extremely wide operating frequency range and very stable operation, through the use of a long, linearly chirped Bragg reflector as the output coupler integrated in a fiber external cavity. A 1.55 mu m strained MQW laser diode is used, with one facet high reflectivity (HR) coated for improved cavity Q, and the other antireflection (AR) coated to allow coupling to the external cavity and suppress Fabry-Perot modes. Near-transform-limited pulses are obtained over a frequency range of 700 MHz around a system operating frequency of 2.488 GHz, with pulsewidths of 50 ps, as required for a practical soliton transmission system. >
TL;DR: In this article, a polymer waveguide thermooptic 2*2 switch with low electric power consumption is demonstrated, which consists of a Mach-Zehnder interferometer with thin-film heaters.
Abstract: A polymer waveguide thermooptic 2*2 switch with low electric power consumption is demonstrated. The switch consists of a Mach-Zehnder interferometer with Cr thin-film heaters. The waveguides are fabricated using acrylic polymers synthesized from deuterated methacrylate and deuterated fluoromethacrylate monomers. The total insertion loss of the switch is 0.6 dB at a wavelength of 1.3 mu m, including fiber coupling losses and waveguide losses. The switching power is as low as 4.8 mW, and the rise and fall times are both 9 ms. >
TL;DR: In this article, a single-mode photo-sensitive waveguide Mach-Zehnder interferometer fabricated in Ge-doped planar silica is reported, and two-millimeter-long identical-wavelength reflection gratings using external UV beams have been written into each arm to demonstrate a four-port bandpass device for the first time using this technology.
Abstract: A single-mode photosensitive waveguide Mach-Zehnder interferometer fabricated in Ge-doped planar silica is reported. Two-millimeter-long identical-wavelength reflection gratings using external UV beams have been written into each arm to demonstrate a four-port bandpass device for the first time using this technology. The imbalance in the arms after writing of the gratings is compensated by laser trimming of one photosensitive arm of the interferometer. A 96.8% reflection of the output port is measured, and 58.8% of the total power available at the input at 1.5558 mu m in the bandpass of 1 nm is transmitted at the second input port after laser trimming. The total fiber-to-fiber insertion loss of the device is measured to be 1.35 dB. >
TL;DR: In this article, a 1.5-mu m semiconductor optical amplifier was used for wavelength conversion at 10 Gb/s, with 0.7-3dB power penalties.
Abstract: Data at 10 Gb/s has been translated from an input signal wavelength to another wavelength, either longer or shorter, using gain compression in a 1.5- mu m semiconductor optical amplifier for wavelength conversion. To achieve operation at such high bit rates, the probe (shifted) input must be intense enough to compress the gain of the amplifier significantly. This reduces the gain recovery time of the amplifier because of probe stimulated emission. A consequence of the intense probe is an extinction ratio deduction. Using moderate input powers, wavelength conversion is achieved over a 17-nm (2-THz) range, with 0.7-3-dB power penalties. >
TL;DR: The bidirectional eigenmode propagation (BEP) as discussed by the authors combines the advantages of the transfer-matrix method for propagation and the mode-matching method (satisfying Maxwell's boundary conditions) at longitudinal large discontinuities for forward and backward travelling eigenvalues including discretized radiation modes.
Abstract: The bidirectional eigenmode propagation (BEP) combines the advantages of the transfer-matrix method for propagation and the mode-matching method (satisfying Maxwell's boundary conditions) at longitudinal large discontinuities for forward and backward travelling eigenvalues including discretized radiation modes. The calculated examples include a grating-assisted codirectional coupler for which 20% radiation losses have been found, and a cleaved waveguide facet with 39% reflected intensity and recapture of radiation modes due to a taperlike structure. The BEP is applicable to various types of optical passive (directional coupler, butt-coupling, taper) and active (DBR-, DFB-, and VCSE-laser, detector) devices with large refractive index differences. >
TL;DR: In this article, a temperature-independent optical waveguide (athermal waveguide) with an optical path length independent of temperature was proposed to cancel out the positive dependence of ordinary optical materials with the negative temperature coefficient of the refractive index of some special materials like polymers.
Abstract: The central waveguide of narrowband optical filters is quite sensitive to temperature. This is an obstacle to the broad use of optical frequency-division multiplexing (FDM) systems. Since this undesired characteristic is caused by the temperature dependence of optical path length in the filter, one can stabilize the filtering characteristics if such dependence is successfully eliminated. Thus, a temperature-independent optical waveguide (athermal waveguide), with an optical path length independent of temperature obtained by canceling out the positive dependence of ordinary optical materials with the negative temperature coefficient of the refractive index of some special materials like polymers, is proposed. The experimental result shows that the temperature dependence of optical path length is reduced to -7% of that of conventional glass waveguides. >
TL;DR: In this article, a monolithically integrated master oscillator power amplifier, M-MOPA, with a flared power amplifier region which radiates in a single diffraction limited lobe to an output power in excess of 2 W CW.
Abstract: The authors fabricated a monolithically integrated master oscillator power amplifier, M-MOPA, with a flared power amplifier region which radiates in a single diffraction limited lobe to an output power in excess of 2 W CW. The radiation pattern is stable with increasing drive current. The spectral output of the M-MOPA is a single longitudinal mode with a side-mode suppression ratio greater than 25 dB. >
TL;DR: In this article, a vertical grating-assisted codirectional coupler laser with rear sampled grating reflector (GCSR) combines single-mode operation over a very wide tuning range of 74 nm with a side-mode suppression of better than 30 dB over most of the wavelength span.
Abstract: A vertical-grating-assisted codirectional coupler laser with rear sampled grating reflector (GCSR laser) combines single-mode operation over a very wide tuning range of 74 nm with a side-mode suppression of better than 30 dB over most of the wavelength span. The total tuning span is limited by the combined bandwidths of the active material gain curve and the envelope of the sampled grating reflection peak spectrum, while the tuning capacity of the directional coupler filter alone is estimated to be at least 140 nm. >
TL;DR: In this article, a simple InP/InGaAsP tapered waveguide is proposed for low-loss coupling between semiconductor photonic devices and single-mode fibers.
Abstract: Low-loss coupling between semiconductor photonic devices and single-mode fibers is achieved using a simple InP/InGaAsP tapered waveguide. The proposed simple structure has a small and nearly square guiding core at its output facet. In this structure, the output field has a non-Gaussian profile, but low-pass filter coupling can be achieved by optimizing the design of the guiding core sizes. The waveguide is composed of a laterally tapered InGaAsP guiding layer and an InP cladding region on an InP substrate, facilitating integration of the waveguide with active devices using conventional processes. The waveguide is shown to have a total insertion loss of 2.6 dB, including a coupling loss of 0.9 dB and large +or-2.5- mu m misalignment tolerance in lateral and vertical directions with single-mode filters. >
TL;DR: A coding technique for improving the sensitivity of optical time domain reflectometry (OTDR) using optical codes derived from Hadamard matrices and does not use correlation is proposed.
Abstract: A coding technique for improving the sensitivity of optical time domain reflectometry (OTDR) is proposed. The technique uses optical codes derived from Hadamard matrices and does not use correlation. The sensitivity realized by this new method is shown to be superior to that obtained using Golay codes. >
TL;DR: In this article, the authors used highly nondegenerate four-wave mixing in a semiconductor traveling-wave optical amplifier to achieve a power penalty of 1.1dB at 10/sup -9/ bit error rate (BER).
Abstract: Wavelength conversion of optical signals over 20 nm is demonstrated using highly nondegenerate four-wave mixing in a semiconductor traveling-wave optical amplifier. This technique has the potential for extremely-high-speed operation and allows continuous tuning of both input and output wavelengths over the amplifier gain bandwidth. It is demonstrated that, even for such a large wavelength conversion range, it is possible to obtain conversion efficiencies in excess of -10 dB and high extinction ratios. The feasibility of the technique is demonstrated by system measurements at 622 Mb/s, showing a 1.1-dB power penalty at 10/sup -9/ bit error rate (BER). >
TL;DR: In this paper, the base collector junction of an InP/InGaAs phototransistor structure for a p-i-n photodetector was fabricated for the first time.
Abstract: Monolithic photoreceivers, using the base-collector junction of an InP/InGaAs phototransistor structure for a p-i-n photodetector, have been fabricated for the first time. Bandwidths as high as 3 GHz and bit rates as high as 5 Gb/s, with sensitivities of -22.5 dBm and -21.5 dBm for light focused on the p-i-n or on the first stage transistor of the preamplifier, respectively, have been achieved. These results represent the highest operating speed demonstrated for any phototransistor-based receiver. >
TL;DR: In this article, an integrated-optic polarization-insensitive wavelength multiplexer that is based on an arrayed-waveguide grating was described, and the multiplexing operation of 16 wavelength channels with a 0.8 nm spacing was confirmed to be independent of the polarization state.
Abstract: An integrated-optic polarization-insensitive wavelength multiplexer that is based on an arrayed-waveguide grating is described. Polarization dependence due to thermal stress was eliminated by depositing an a-Si birefringence compensation film on the arrayed-waveguide. The multiplexing operation of 16 wavelength channels with a 0.8 nm spacing was confirmed to be independent of the polarization state. >
TL;DR: In this article, a multiquantum-well optical amplifier for 1.5-mu m wavelength operation using alternating tensile and compressively strained wells in the active region is described.
Abstract: A multiquantum-well optical amplifier for 1.5- mu m wavelength operation using alternating tensile and compressively strained wells in the active region is described. For each bias level measured, the polarization sensitivity of the amplifier gain is 1 dB or less averaged over the gain bandwidth. This amplifier is suitable for integration with other optical devices in photonic integrated circuits which require polarization-independent gain. >
TL;DR: In this article, a fiber chromatic dispersion compensation technique with optical single-sideband (SSB) transmission in optical homodyne detection systems is described, which is demonstrated in a 6-Gb/s SSB phase-shift-keying (PSK) detection system equivalent experiment.
Abstract: A fiber chromatic dispersion compensation technique with optical single-sideband (SSB) transmission in optical homodyne detection systems is described. The chromatic dispersion compensation technique is demonstrated in a 6-Gb/s SSB phase-shift-keying (PSK) homodyne detection system equivalent experiment. A 270-km conventional single-mode fiber is used as a transmission medium at 1.55 mu m, and a microstrip line is used as a delay equalizer. The effect of compensating for the chromatic dispersion with the microstrip line is verified by improvement of eye-opening. >