Showing papers on "Fiber laser published in 1982"
TL;DR: An all-fiber ring resonator, constructed from a single strand of single-mode optical fiber and a directional coupler, is shown to have a low threshold for stimulated Brillouin laser action.
Abstract: An all-fiber ring resonator, constructed from a single strand of single-mode optical fiber and a directional coupler, is shown to have a low threshold for stimulated Brillouin laser action. The 10-m-perimeter fiber ring resonator has a low round-trip loss of under 3.5% and an inherent pump-power enhancement of approximately 30. Lasing threshold for the 4.0-microm-core fiber occurred with a pump power of 0.56 mW at lambda = 6328 A and 1.74 mW at lambda = 5145 A.
202 citations
TL;DR: A simple method to selectively etch a fiber end to produce a conical lens whose base coincides with the fiber core is proposed and it is found that high coupling efficiency is expected in cases of practical interest.
Abstract: Coupling efficiency between a laser diode and a single-mode fiber can be greatly increased by using a lensing scheme to match their respective modes. We propose a simple method to selectively etch a fiber end to produce a conical lens whose base coincides with the fiber core. If needed, this lens may be fire polished or arc melted into a hemispherical lens of the same diameter. We present a general theoretical design of both these lenses. We find that high coupling efficiency is expected in cases of practical interest. Initial experimental results are reported in which coupling losses as low as 3 dB were obtained.
128 citations
TL;DR: Optical feedback effects on spectral properties of a semiconductor laser diode coupled to a single-mode fiber cavity are investigated in this article, where Linewidth reduction from 6 MHz to less than 30 kHz and frequency stability improvement with increasing feedback are reported.
Abstract: Optical feedback effects on spectral properties of a semiconductor laser diode coupled to a single-mode fiber cavity are investigated. Linewidth reduction from 6 MHz to less than 30 kHz and frequency stability improvement with increasing feedback are reported. Experiments are in good agreement with theory for short fiber cavities.
74 citations
TL;DR: In this paper, the authors describe the improvement in mode partition noise characteristics when a laser light is injected into a laser diode modulated at 400 Mbits/s, and the relationship between the half-power width of the spectral envelope and signal-to-noise ratio (SNR) degradation is obtained at 20 km fiber length.
Abstract: This paper describes the improvement in mode partition noise characteristics when a laser light is injected into a laser diode modulated at 400 Mbits/s. A single-mode fiber transmission experiment is carried out for the 1.5 μm region. A 20 km repeater spacing at 400 Mbit/s modulation is achieved by LD light injection. The center longitudinal mode power is increased to 94 percent of the total modes. Relative noise in the center longitudinal mode is improved 30 dB by optical injection of -18.2 dBm. However, the mode partition noise generated by noninjected modes is not completely suppressed. The relationship between the half-power width of the spectral envelope and signal-to-noise ratio (SNR) degradation is obtained at 20 km fiber length. If 3 dB excess SNR degradation is allowed for the mode partition noise, then the necessary half-power width of the spectral envelope is less than 0.6 nm.
70 citations
Patent•
15 Oct 1982
TL;DR: In this article, a unitary connector for coupling a laser beam in proper alignment with an optical fiber is presented. But the connector is not designed for the case of misalignment of the laser beam.
Abstract: The present invention is directed to a novel laser catheter assembly including a unitary connector for coupling a laser beam in proper alignment with an optical fiber. An optical fiber assembly comprising an optical fiber interposed within a catheter tube is permanently mounted to the connector which is of one-piece molded construction. A presently preferred embodiment of the connector has an axial bore at the proximal end thereof of substantially the same diameter as the optical fiber, and a second bore larger than the diameter of the fiber, the second bore being in communication with a source of coolant. In a preferred embodiment the connector is further provided with a cavity in the area about the proximal tip of the optical fiber so as to minimize fouling of the fiber tip in the event of misalignment of the laser beam.
51 citations
TL;DR: A novel method to determine quantitatively the optical feedback from a fiber to a laser is developed and is applied to evaluate the feedback of several standard laser-to-fiber coupling techniques.
Abstract: The power emission from a semiconductor laser rear facet changes characteristically if a reflecting device, e.g., an optical fiber, is placed opposite the laser front facet. Based on this power change a novel method to determine quantitatively the optical feedback from a fiber to a laser is developed. The method is applied to evaluate the feedback of several standard laser-to-fiber coupling techniques.
39 citations
TL;DR: In this paper, phase-matched two-wave sum-frequency light has been observed in optical fibers using a Nd:YAG laser by simultaneous mode-locking and Q-switching or only Q -switching operation.
Abstract: The generation of phase-matched two-wave sum-frequency light has been observed in optical fibers. A Nd:YAG laser by simultaneous mode-locking and Q -switching or only Q -switching operation is used as a pump laser. The input power dependence and fiber length dependence of the sum-frequency light are investigated in the two pumping methods. The observed coherence length for the sum-frequency light generation is about 200 m.
35 citations
17 Dec 1982
TL;DR: In this article, a 20 mJ pulse from a Nd:YAG laser is compressed from 20 nsec to 3 nec in a fiber 7 feet long by stimulated Brillouin scattering in a tapered glass fiber.
Abstract: Laser pulse compression by the process of stimulated Brillouin scattering in a tapered glass fiber is discussed. A 20 mJ pulse from a Nd:YAG laser is compressed from 20 nsec to 3 nec in a fiber 7 feet long.© (1982) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
33 citations
TL;DR: In vivo recordings of coronary and aortic blood velocity are produced by performing a fast Fourier transform (FET) in real time.
Abstract: Laser Doppler anemometry has been used to measure blood velocities by using a fine fiber optic probe both to deliver laser light into the blood and to receive reflected light from red blood cells at the tip of the probe. In vitro, with the probe aligned in the direction of flow, nonlinear calibration is possible to velocities of 15 cm/s in a 3 mm diameter vessel. When the probe is aligned against the flow, measurement of velocity is linear to at least 1 m/s. In vivo recordings of coronary and aortic blood velocity are produced by performing a fast Fourier transform (FET) in real time.
32 citations
TL;DR: In this article, the applications of AlGaAs semiconductor laser preamplifier and linear repeaters in single mode optical fiber transmission systems were studied through the baseband signal-to-noise ratio and bit error rate performance measurement.
Abstract: The applications of AlGaAs semiconductor laser preamplifier and linear repeaters in single mode optical fiber transmission systems were studied through the baseband signal-to-noise ratio and bit error rate performance measurement. Experiments were carried out with the Fabry-Perot cavity laser amplifiers whose characteristics are improved by reducing the input mirror reflectivity to 6 percent. The use of a preamplifier improves the minimum detectable power by 7.4 dB over the Si-APD direct detection level when the received signal is amplified by 30 dB before photodetection. The use of two linear repeaters increases the regenerative repeater gain by 37 dB. These experimental results are in good agreement with theoretical predictions based on the photon statistic master equation analysis.
32 citations
TL;DR: In this article, the authors describe the improvement in mode partition noise characteristics when a laser light is injected into a laser diode modulated at 400 Mbits/s, and the relationship between the half-power width of the spectral envelope and signal-to-noise ratio (SNR) degradation is obtained at 20 km fiber length.
Abstract: This paper describes the improvement in mode partition noise characteristics when a laser light is injected into a laser diode modulated at 400 Mbits/s. A single-mode fiber transmission experiment is carried out for the 1.5 µm region. A 20 km repeater spacing at 400 Mbit/s modulation is achieved by LD light injection. The center longitudinal mode power is increased to 94 percent of the total modes. Relative noise in the center longitudinal mode is improved 30 dB by optical injection of -18.2 dBm. However, the mode partition noise generated by noninjected modes is not completely suppressed. The relationship between the half-power width of the spectral envelope and signal-to-noise ratio (SNR) degradation is obtained at 20 km fiber length. If 3 dB excess SNR degradation is allowed for the mode partition noise, then the necessary half-power width of the spectral envelope is less than 0.6 nm.
TL;DR: In this article, a novel method to achieve phase matched light amplification in a birefringent fiber via the three-wave mixing is proposed by using frequency shift change due to the stress applied to the fiber.
Abstract: A novel method to achieve phase‐matched light amplification in a birefringent fiber via the three‐wave mixing is proposed by using frequency shift change due to the stress applied to the fiber. It is confirmed that the signal power from a cw laser diode at λ=1.292 μm is amplified by 6.1×103 times in the birefringent fiber pumped with a Q‐switched Nd: yttrium aluminum garnet laser at λ=1.064 μm. This will provide a new fiber‐optic light signal amplifier having a good tolerance for variation of signal wavelengths.
Patent•
01 Jul 1982TL;DR: A monitor device for use in a laser system transmitting laser light through an optical fiber includes a heat-sensitive element which produces an output to monitor the laser system, the element being provided in a predetermined area of the fiber as discussed by the authors.
Abstract: A monitor device for use in a laser system transmitting laser light through an optical fiber includes a heat-sensitive element which produces an output to monitor the laser system, the element being provided in a predetermined area of the fiber.
TL;DR: A multispot photocoagulation system equipped with a fiber bundle scanner is developed for the treatment of widely spread port wine stain and the output patterns from two bundles of graded-index and step-index fibers are analyzed experimentally.
Abstract: A multispot photocoagulation system equipped with a fiber bundle scanner is developed for the treatment of widely spread port wine stain. The laser transmission system consists of multiple quartz fiber, the input ends of which are aligned and driven by a stepper motor across a high-power argon laser beam. The output ends are arranged in a hexagonal close-packed array from which the diverging laser beam successively irradiates different spots of a lesion without the use of a mechanical scan over the lesion. The output patterns from two bundles of graded-index and step-index fibers are analyzed experimentally.
TL;DR: In this article, the authors describe important studies necessary to design submarine optical fiber cables, including a study for deciding the optimum singlemode fiber parameters to suppress losses during cabling, cable laying, and so on.
Abstract: This paper describes important studies necessary to design submarine optical fiber cables. These include a study for deciding the optimum single-mode fiber parameters to suppress losses during cabling, cable laying, and so on. It also includes a study on the necessary fiber proof test conditions to prevent fiber breakage during cable handling, that is, during cable laying and recovery and to assure long-term fiber reliability. Submarine optical fiber cable sea trial results are also stated for cables designed applying these studies.
TL;DR: In this article, an optical probe has been developed for acoustic surface waves using singlemode fiber to illuminate the sample, which has an effective spot size of 4 μm without the use of focusing lenses.
Abstract: An optical probe has been developed for acoustic surface waves using single‐mode fiber to illuminate the sample. The scanned fiber probe has an effective spot size of 4 μm without the use of focusing lenses. 34% of the incident light re‐enters the fiber from a specular reflector. The signal from the sample is combined with a reference in a single fiber, eliminating misalignment in the interferometric measurement. Experimental results are presented for a LiNbO3 focused transducer surface acoustic wave (SAW) device. On this device, the probe exhibits 60‐dB dynamic range and 3×10−2 A minimum sensitivity. The resolution, sensitivity, and flexibility of the fiber probe make it applicable to crack detection in nondestructive testing.
TL;DR: In this paper, a CO2 laser beam was transmitted through a single-crystal CsBr fiber with losses of 0.3∼0.4 dB/m.
Abstract: Transmission of a CO2 laser beam by single‐crystal CsBr fibers with losses of 0.3∼0.4 dB/m has been investigated. Transmission losses including the fiber losses and joint losses were less than 30% per meter. Using a 55‐W CO2 laser as a source power, a 47‐W continuous laser beam has been transmitted through 1‐mm‐diam fiber without any degradation of the fiber.
17 Dec 1982
TL;DR: In this paper, the power transmission capabilities of polycrystalline (PC) KRS-5 fibers have remarkably increased since the first report by researchers at Hughes Research Laboratories, where the power density at the fiber input end is 36 KW/cm2 and remarkable damage is not observed.
Abstract: Power transmitting capabilities of polycrystalline (PC) KRS-5 fibers have remarkably increased since the first report by researchers at Hughes Research Laboratories. Maximally transmitted power of CW CO2 laser beam through PC KRS-5 fiber has reached up to about 100W. The power density at the fiber input end is 36 KW/cm2 and remarkable damage is not observed. Mechanical properties of PC KRS-5 fiber is superior to any other PC fiber, therefore PC KRS-5 fiber is a hopeful waveguide for the practical use of CO2 laser power transmission. And also it is applicable for IR sensor systems in a short range. When the power transmission capabilities of PC KRS-5 fiber will be attained up to several hundreds watt, it will be widely used in the field of the CO2 laser machining.© (1982) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
TL;DR: In this article, the integral phase change of the laser light propagation into the vibrating fiber optic is evaluated and a mechanical system was designed to exactly delimitate the part of the optical fiber which is subjected to vibration.
Abstract: A comparison is reported between the dynamical response of a single-mode fiber optic and resistive strain gages in the frequency range 25-250 Hz. The integral phase change of the laser light propagation into the vibrating fiber optic is evaluated. A mechanical system was designed to exactly delimitate the part of the optical fiber which is subjected to vibration. The frequency spectrum of the phase change signal and the resistive strain gage signal show equivalent behavior. This result is in good agreement with the theoretically expected values and confirms the validity of the analysis performed.
TL;DR: A simple active control system is described that maintains the output of a single-mode fiber at prescribed polarization and intensity, thus counteracting erratic birefringeance effects in the fiber that are due to temperature drift and mechanical disturbances.
Abstract: A simple active control system is described that maintains the output of a single-mode fiber at prescribed polarization and intensity, thus counteracting erratic birefringeance effects in the fiber that are due to temperature drift and mechanical disturbances. Whereas the system of Ulrich [Appl. Phys. Lett. 35, 840 (1979)] controls two polarization parameters by means of two interdependent control loops, ours controls only one parameter and requires only a single control loop. The resulting considerable reduction of optical and electronic system complexity is realized at the expense of about 30-50% of input light intensity.
11 Dec 1982
TL;DR: In this paper, the intended fiber-optic applications for both short and long-wavelength single-mode diode lasers are discussed, and major types of singlemode devices are grouped and described in two sections.
Abstract: The intended fiber-optic applications for both short- and long-wavelength single-mode diode lasers are discussed. Major types of single-mode devices are grouped and described in two sections: low-power (3-7 mW/facet) lasers and high-power (10-40 mW/facet) lasers. The low-power laser section contains principles of mode stabilization, and a treatment in parallel of AlGaAs and InGaAsP buried-mesa, non-planar-substrate and laterally-lossy devices. The high-power laser section contains the various means of achieving high-power reliable single-mode operation and a description and comparison of major types of high-power AlGaAs devices. Emphasis is placed on the performance of the constricted double-heterojunction large-optical-cavity (CDH-LOC) laser. A brief discussion of single-mode stabilization and device dynamic behavior is also presented.
TL;DR: In this paper, a multiple ruby laser system is used to provide intense, extremely short (30 ns) highly monochromatic light pulses for high speed photography, and the light output from the lasers is transmitted to the two optical systems with fiber optic light guides.
Abstract: A multiple ruby laser system is used to provide intense, extremely short (30 ns) highly monochromatic light pulses for high speed photography. The light output from the lasers is transmitted to the two optical systems with fiber optic light guides. The ruby lasers are employed with a conventional Cranz-Schardin system in dynamic photoelastic studies of stress waves and in studies of crack branching in tempered glass. The ruby lasers are employed with an unorthodox Cranz-Schardin system in ballistics studies of armor penetration. Of particular importance is the use of a microprocessor which provides precise synchronization by computing in real time the anticipated arrival time and controlling the Q-switching of the lasers. Variations in projectile velocity due to projectile weight, charge density, and drag are accommodated by programming the microprocessor.
TL;DR: In this paper, the dual channel triggering of a spark gap switch by fiberoptic transported ruby laser radiation is discussed, and the correlation of this behavior with the space charge build up in the slightly over-volted gap is discussed.
Abstract: The dual channel triggering of a spark gap switch by fiberoptic transported ruby laser radiation is discussed. The spark gap is the output switch of a 20-ns water dielectric Blumlein generator. The Blumlein generator is pulse charged in approximately 250 ns by a three-stage Marx bank to 150 kV. The spark gap is operated at a pressure of 2540 torr with a mixture of Ar and N2 gas and an electrode separation of 2 cm. Two 1-mm diameter quartz optical fibers are used to transport 2 2-MW laser beams into the spark gap onto points 6 cm apart on the target electrode. The two beams are obtained by optical splitting of the output of a single laser. Under appropriate conditions, two arc channels are initiated by the laser beams along their paths. A small improvement in current rise time for dual channel events over single channel events is observed. Moreover, the number of successful dual channel events is observed to depend on the time of laser entry with reference to the beginning of the charging pulse, and not the gap polarity. The correlation of this behavior with the space charge build up in the slightly over-volted gap is discussed.
01 Jun 1982
TL;DR: Surgical advances in the application of lasers would be assisted by engineering developments such as a tuneable laser, a flexible carbon dioxide transmission fiber, miniaturization, reduction in cost, improvement in cooling systems, and portability of the laser surgical instrument.
Abstract: Because of an ability to coagulate, ablate, or vaporize tissue, argon, CO 2 , and Nd:YAG lasers have been employed extensively in surgery. The capability of transmitting argon and neodymium YAG energy through a flexible fiber which may be inserted in a fiberoptic instrument allows the application of the laser in a number of anatomic areas without the need for an incision. Extensive application has been made in utilizing laser techniques in treating lesions of the gastrointestinal tract, skin, central nervous system, bladder and urethra, spine, joints, ear, nose and throat, and in general surgery to provide control of bleeding. Surgical advances in the application of lasers would be assisted by engineering developments such as a tuneable laser, a flexible carbon dioxide transmission fiber, miniaturization, reduction in cost, improvement in cooling systems, and portability of the laser surgical instrument.
13 Apr 1982
TL;DR: In this article, the authors developed a more easily spliced multicore fiber: bunch fiber, which can be used to reduce the diameter of the cable by up to 50% compared with using ordinary monocore fiber.
Abstract: Fabrication of an ultrahigh density cable is important, especially for subscriber loops. By using ultrahigh density cable, low cost optical transmission lines may be constructed. A multicore optical fiber1 100-200 μm in diameter is suitable. By using multicore fiber the cable diameter can be reduced drastically, compared with using ordinary monocore fiber. However ordinary multicore fiber is difficult to splice, because due to its circular construction, it is difficult to determine proper alignment. Splicing is difficult because the fibers must be rotated to achieve proper alignment. To overcome this, we developed a more easily spliced multicore fiber: bunch fiber.
TL;DR: In this paper, the authors describe an attainable repeater spacing for a high bit-rate single-mode fiber-optic transmission in the 1.55 μm wavelength region where laser mode partition noise comes to be significant.
Abstract: This paper describes an attainable repeater spacing for a high bit-rate single-mode fiber-optic transmission in the 1.55 μm wavelength region where laser mode partition noise comes to be significant. An expression for evaluating mode partition noise is given as the form involving the influence of laser spectral fluctuations under high bit-rate modulation, together with the intersymbol interference and the equalized pulse shape in tile optical receiver. After the validity of its numerical results is confirmed experimentally, the resulting evaluation of laser mode partition noise is connected to a systematic discussion on the attainable repeater spacing of a 280 Mbit/s fiber-optic transmission system operating at 1.55 μm, along with fiber loss versus dispersion tradeoffs. This discussion permits the attainable repeater spacing to be 60-70 km for the combination of a laser diode with 1.5-2.0 nm spectrum broadening and a fiber with the loss of 0.5 dB/km and the dispersion of 4-6 ps/km - nm.
TL;DR: A ray trace model is developed which describes the intensity and phase characteristics of a forward-scattered pattern generated by transversely illuminating a silicone-coated fused-silica fiber with a laser beam.
Abstract: A ray trace model is developed which describes the intensity and phase characteristics of a forward-scattered pattern generated by transversely illuminating a silicone-coated fused-silica fiber with a laser beam. The dominant characteristic of this pattern is a region of interference fringes which result from the interference of rays traveling through the fibers and the coating and rays traveling through the coating only. The location of the fringe region and the fringe period depends on fiber and coating parameters and the fiber eccentricity within the coating. The parameter sensitivities are examined, and the model results compared to experimentally measured characteristics of the light scattering pattern.
TL;DR: Optical feedback effects on spectral properties of a semiconductor laser diode coupled to a single-mode fiber cavity are investigated in this article, where Linewidth reduction from 6 MHz to less than 30 kHz and frequency stability improvement with increasing feedback are reported.
Abstract: Optical feedback effects on spectral properties of a semiconductor laser diode coupled to a single-mode fiber cavity are investigated. Linewidth reduction from 6 MHz to less than 30 kHz and frequency stability improvement with increasing feedback are reported. Experiments are in good agreement with theory for short fiber cavities.