Showing papers on "Dispersion-shifted fiber published in 2006"
TL;DR: The robust single-transverse-mode propagation in a passive 100 microm core fiber with a similar design reveals the potential of extended large-mode-area photonic crystal fibers.
Abstract: We report on an ytterbium-doped photonic crystal fiber with a core diameter of 60 μm and mode-field-area of ~2000 μm2 of the emitted fundamental mode. Together with the short absorption length of 0.5 m this fiber possesses a record low nonlinearity which makes this fiber predestinated for the amplification of short laser pulses to very high peak powers. In a first continuous-wave experiment a power of 320 W has been extracted corresponding to 550 W per meter. To our knowledge this represents the highest power per unit length ever reported for fiber lasers. Furthermore, the robust single-transverse-mode propagation in a passive 100 μm core fiber with a similar design reveals the potential of extended large-mode-area photonic crystal fibers.
358 citations
TL;DR: It is shown using simulations that a combination of Orthogonal Frequency Division Multiplexing (OFDM) and Optical Single Sideband Modulation (OSSB) can be used to adaptively compensate for chromatic dispersion in ultra-long-haul 10 Gbps Standard Single-Mode Fiber links.
Abstract: We show using simulations that a combination of Orthogonal Frequency Division Multiplexing (OFDM) and Optical Single Sideband Modulation (OSSB) can be used to adaptively compensate for chromatic dispersion in ultra-long-haul 10 Gbps Standard Single-Mode Fiber (S-SMF) links. Additionally, for optical noise limited systems with Forward-Error Correction, OFDM can tolerate an Optical Signal to Noise Ratio (OSNR) 0.5 dB higher than NRZ systems providing the optical carrier is suppressed.
353 citations
TL;DR: A simple subwavelength-diameter plastic wire, similar to an optical fiber, for guiding a terahertz wave with a low attenuation constant is reported, with direct free-space coupling efficiency as high as 20% can be achieved by use of an off-axis parabolic mirror.
Abstract: We report a simple subwavelength-diameter plastic wire, similar to an optical fiber, for guiding a terahertz wave with a low attenuation constant. With a large wavelength-to-fiber-core ratio, the fractional power delivered inside the lossy core is reduced, thus lowering the effective fiber attenuation constant. In our experiment we adopt a polyethylene fiber with a 200 µm diameter for guiding terahertz waves in the frequency range near 0.3 THz in which the attenuation constant is reduced to of the order of or less than 0.01 cm−1. Direct free-space coupling efficiency as high as 20% can be achieved by use of an off-axis parabolic mirror. Furthermore, all the plastic wires are readily available, with no need for complex or expensive fabrication.
283 citations
TL;DR: The first demonstration of the only electronic phase locking technique that doesn't require a reference beam is reported, and the measured phase error is lambda/20.
Abstract: A novel, highly accurate, all electronic technique for phase locking arrays of optical fibers is demonstrated. We report the first demonstration of the only electronic phase locking technique that doesn’t require a reference beam. The measured phase error is λ/20. Excellent phase locking has been demonstrated for fiber amplifier arrays.
197 citations
TL;DR: A fiber-based frequency comb system consisting of a simple mode-locked fiber laser and a backward pumping amplifier combined with a highly nonlinear fiber with a short zerodispersion wavelength is developed, and the signal to noise ratio of the obtained carrier-envelope-offset frequency beat is larger than 45 dB at a bandwidth of 100 kHz.
Abstract: We have developed a fiber-based frequency comb system consisting of a simple mode-locked fiber laser and a backward pumping amplifier combined with a highly nonlinear fiber with a short zerodispersion wavelength. As a result, the signal to noise ratio of the obtained carrier-envelope-offset frequency beat is larger than 45 dB at a bandwidth of 100 kHz. Furthermore, we have succeeded in measuring the optical frequencies of a 1542-nm acetylene-stabilized laser and a 532-nm iodinestabilized Nd:YAG laser continuously for more than one week using the fiber-based comb system. The long-term measurement revealed that the frequency stability of the iodine-stabilized laser was 5.7 x 10(-15) with 100 000 s averaging.
183 citations
TL;DR: In this paper, the authors observed both extremely slow and superluminal pulse propagation speeds at room temperature in an erbium-doped fiber (EDF) with varying powers of a 980 nm pump.
Abstract: We observe both extremely slow and superluminal pulse propagation speeds at room temperature in an erbium-doped fiber (EDF). A signal at 1550 nm is sent through an erbium-doped fiber with varying powers of a 980 nm pump. The degree of signal delay or advancement is found to depend significantly on the pump intensity. We observe a maximum fractional advancement of 0.124 and a maximum fractional delay of 0.089. The effect is demonstrated both for a sinusoidally modulated signal and for Gaussian pulses. The ability to control the sign and magnitude of the pulse velocity could have important implications for applications in photonics.
178 citations
TL;DR: By transforming the optical fiber span into an ultralong cavity laser, this work experimentally demonstrate quasilossless transmission over long (up to 75 km) distances and virtually zero signal power variation over shorter spans, opening the way for the practical implementation of integrable nonlinear systems in optical fiber.
Abstract: By transforming the optical fiber span into an ultralong cavity laser, we experimentally demonstrate quasilossless transmission over long (up to 75 km) distances and virtually zero signal power variation over shorter (up to 20 km) spans, opening the way for the practical implementation of integrable nonlinear systems in optical fiber. As a by-product of our technique, the longest ever laser (to the best of our knowledge) has been implemented, with a cavity length of 75 km. A simple theory of the lossless fiber span, in excellent agreement with the observed results, is presented.
171 citations
TL;DR: A wavelength-spacing tunable multiwavelength erbium-doped fiber laser based on degenerate four-wave mixing in a dispersion-shifted fiber incorporating multiple-fiber Bragg gratings is experimentally demonstrated.
Abstract: We experimentally demonstrate a wavelength-spacing tunable multiwavelength erbium-doped fiber laser based on degenerate four-wave mixing in a dispersion-shifted fiber incorporating multiple-fiber Bragg gratings. We have achieved stable operation of the multiwavelength erbium-doped fiber laser, which has 0.8 nm spacing ten-channel lasing wavelengths and a high extinction ratio of more than ∼45 dB, at room temperature. The output power of the multiwavelength erbium-doped fiber laser is stable, so the peak fluctuation is less than ∼0.2 dB. By changing the properties such as loss and polarization state of multiple fiber Bragg grating cavities, we can exercise flexible control of the wavelength spacing of the multiwavelength output. We can also obtain switchable multiwavelength lasing operation by elimination of the effects of alternate single-fiber Bragg gratings.
163 citations
TL;DR: The results demonstrate that the liquid-core PCF is capable to generate dramatically broadened supercontinua in a range from 700 nm to more than 2500 nm when pumping at 1.55 mum with subpicosecond pulses.
Abstract: We have numerically studied a hollow-core photonic crystal fiber, with its core filled with highly nonlinear liquids such as carbon disulfide and nitrobenzene Calculations show that the fiber has an extremely high nonlinear parameter γ on the order of 24/W/m at 155 μm The group velocity dispersion of this fiber exhibits an anomalous region in the near-infrared, and its zero-dispersion wavelength is around 155 μm This leads to potentially significant improvements and a large bandwidth in supercontinuum generation The spectral properties of the supercontinuum generation in liquid-core photonic crystal fibers are simulated by solving the generalized nonlinear Schrodinger equation The results demonstrate that the liquid-core PCF is capable to generate dramatically broadened supercontinua in a range from 700 nm to more than 2500 nm when pumping at 155 μm with subpicosecond pulses
152 citations
TL;DR: It is demonstrated that the relative group velocity, the chromatic dispersion and the dispersion slope of a sample fiber can be obtained very accurately regardless of the zero-dispersion wavelength (ZDW) of a samples after frequency dependent optical phase was directly retrieved from a spectral interferogram.
Abstract: We present a versatile and accurate chromatic dispersion measurement method for single mode optical fibers over a wide spectral range (200 nm) using a spectral domain white light interferometer. This technique is based on spectral interferometry with a Mach-Zehnder interferometer setup and a broad band light source. It takes less than a second to obtain a spectral interferogram for a few tens of centimeter length fiber sample. We have demonstrated that the relative group velocity, the chromatic dispersion and the dispersion slope of a sample fiber can be obtained very accurately regardless of the zero-dispersion wavelength (ZDW) of a sample after frequency dependent optical phase was directly retrieved from a spectral interferogram. The measured results with our proposed method were compared with those obtained with a conventional time-domain dispersion measurement method. A good agreement between those results indicates that our proposed method can measure the chromatic dispersion of a short length optical fiber with very high accuracy.
143 citations
TL;DR: A simple technique to obtain stable room temperature multiwavelength lasing in an erbium-doped fiber laser by the inhomogeneous loss mechanism by incorporating a section of highly nonlinear fiber and a Fabry-Perot filter in the laser cavity is demonstrated.
Abstract: We demonstrated a simple technique to obtain stable room temperature multiwavelength lasing in an erbium-doped fiber laser by the inhomogeneous loss mechanism. Successful reduction of the cross-gain saturation in erbium-doped fiber was achieved by incorporating a section of highly nonlinear fiber (HNLF) and a Fabry-Perot filter (FPF) in the laser cavity. More than 70 wavelengths simultaneous lasing were observed with the same frequency space of 25GHz. The laser had a total output power of ~3.2dBm, a bandwidth of 0.012nm (~1.5GHz) and a signal-to-spontaneous-noise ratio of ~44dB. Furthermore, the total output power can be increased to more than 190mW by moving the output port right after the EDFA.
TL;DR: A systematic process of theoretical design and experimental fabrication of the large mode area and large negative dispersion photonic crystal fiber is presented and an easily fabricated fiber structure is proposed.
Abstract: We present a systematic process of theoretical design and experimental fabrication of the large mode area and large negative dispersion photonic crystal fiber. An easily fabricated fiber structure is proposed. The influence of structure parameters deviations from the design on the chromatic dispersion are evaluated and a design rule is given. Finally our fabricated fiber and test results are demonstrated. The measured effective area of inner core mode is 40.7 μm2 which is the largest effective area of high negative dispersion photonic crystal fibers that have been experimentally fabricated. The measured peak dispersion is -666.2ps/(nm.km) and the bandwidth is 40nm.
TL;DR: An asymmetric long period fiber grating with a large attenuation of −47.39dB and a low insertion loss of 0.34dB is fabricated by use of focused CO2 laser beam to carve periodic grooves on one side of the optical fiber.
Abstract: An asymmetric long period fiber grating (LPFG) with a large attenuation of −47.39dB and a low insertion loss of 0.34dB is fabricated by use of focused CO2 laser beam to carve periodic grooves on one side of the optical fiber. Such periodic grooves and the stretch-induced periodic microbends can effectively enhance the refractive index modulation and increase the average strain sensitivity of the resonant wavelength of the LPFG to −102.89nm∕me. The resonant wavelength and the peak attenuation of the LPFG can be tuned by ∼12nm and ∼20dB, respectively, by the application of a stretching force.
TL;DR: In this paper, the beam quality factor (or M2-parameter) for linearly polarized (LP)-modes of a step-index fiber is calculated in a closed form, as a function of the fiber V-number.
Abstract: The beam quality factor (or M2-parameter) for linearly polarized (LP)-modes of a step-index fiber is calculated in a closed form, as a function of the fiber V-number. It is shown that M2 sharply peaks for all fiber modes when they are close to cutoff. Particularly simple expressions are derived in the limit Vrarrinfin. Two practically important coherent superpositions of modes are considered for which the degree of degradation of the beam quality due to the higher order mode content is calculated. The reported results can be useful for designing large-core high-power fiber lasers, amplifiers, and fiber-based beam delivery systems, when preservation of the spatial beam quality is important
TL;DR: An all-solid (nonholey), silica-based fiber with anomalous dispersion at wavelengths where silica material dispersion is negative is demonstrated, achieved by exploiting the enhanced dispersion engineering capabilities of higher-order modes in a fiber.
Abstract: We demonstrate an all-solid (nonholey), silica-based fiber with anomalous dispersion at wavelengths where silica material dispersion is negative. This is achieved by exploiting the enhanced dispersion engineering capabilities of higher-order modes in a fiber, yielding +60 ps/nm km dispersion at 1080 nm. By coupling to the desired higher-order mode with low-loss in-fiber gratings, we realize a 5 m long fiber module with a 300 fs/nm dispersion that yields a 1 dB bandwidth of 51 nm with an insertion loss of ∼0.1 dB at the center wavelength of 1080 nm. We demonstrate its functionality as a critical enabler for an all-fiber, Yb-based, mode-locked femtosecond ring laser.
TL;DR: A theoretical scheme for a new surface plasmon-polariton (SPP) fiber sensor with a fiber Bragg grating imprinted into the fiber core for SPP excitation is presented for the first time to the authors' knowledge.
Abstract: A theoretical scheme for a new surface plasmon-polariton (SPP) fiber sensor with a fiber Bragg grating imprinted into the fiber core for SPP excitation is presented for the first time to our knowledge. In our scheme the energy in the fiber core mode can be transferred to a SPP with high efficiency by means of a properly designed short-period fiber Bragg grating (SPG). Developed for the cylindrical (fiber) geometry, our scheme without loss of generality can be applied to a planar geometry. Our simulations are based on the coupled-mode method and are performed at telecommunications wavelengths.
TL;DR: In this article, a novel technique for optical multiplication of a millimeter-wave carrier is presented, which utilizes optical four-wave mixing (FWM) in highly nonlinear fiber (HNLF) and the filtering properties of matched fiber Bragg gratings (FBGs).
Abstract: A novel technique for optical multiplication of a millimeter-wave carrier is presented. It utilizes optical four-wave mixing (FWM) in a highly nonlinear fiber (HNLF) and the filtering properties of matched fiber Bragg gratings (FBGs). The technique includes a sixfold electrical frequency multiplication in the optical domain. In this experiment, the multiplicator is driven electronically at 6.67 GHz, and the created millimeter wave has a frequency of 40 GHz. The generated carrier has a linewidth lower than 3 Hz and a carrier to noise ratio exceeding 50 dB. Furthermore, successful data transmission over the optical fiber of 2.5 Gb/s on the generated millimeter-wave carrier was performed.
TL;DR: Dual-concentric-core photonic crystal fibers having larger negative dispersion coefficient as well as compensating for dispersion slope of SMFs in the entire C band with large effective area can be designed.
Abstract: Chromatic dispersion profile of dual-concentric-core photonic crystal fibers is optimized for broadband dispersion compensation of single mode fibers (SMFs) by using genetic algorithm incorporated with full-vector finite-element method. From the numerical results presented here, it is found that by increasing the distance between central core and outer ring core, larger negative dispersion coefficient and better dispersion slope compensation are possible. There is a tradeoff between the magnitude of negative dispersion coefficient and dispersion slope compensation due to the concave dispersion profile of dual-concentric-core photonic crystal fibers. In spite of the tradeoff, dual-concentric-core photonic crystal fibers having larger negative dispersion coefficient as well as compensating for dispersion slope of SMFs in the entire C band with large effective area can be designed.
TL;DR: A novel linear filtering scheme based on ultrafast all-optical differentiation for re-shaping of ultrashort pulses generated from a mode-locked laser into flat-top pulses is proposed and demonstrated using simple all-fiber optical filters.
Abstract: We propose a novel linear filtering scheme based on ultrafast all-optical differentiation for re-shaping of ultrashort pulses generated from a mode-locked laser into flat-top pulses. The technique is demonstrated using simple all-fiber optical filters, more specifically uniform long period fiber gratings (LPGs) operated in transmission. The large bandwidth typical for these fiber filters allows scaling the technique to the sub-picosecond regime. In the experiments reported here, 600-fs and 1.8-ps Gaussian-like optical pulses (@ 1535 nm) have been re-shaped into 1-ps and 3.2-ps flat-top pulses, respectively, using a single 9-cm long uniform LPG.
TL;DR: In this article, a neodymium fiber laser incorporating an all-solid photonic bandgap fiber was used to suppress the four-level laser transition 4F3/2-4I11/2.
Abstract: We report a neodymium fiber laser incorporating an all-solid photonic bandgap fiber to suppress the four-level laser transition 4F3/2-4I11/2. We demonstrate lasing at 907 nm on the three-level transition 4F3/2-4I9/2 when pumping at 808 nm. The maximum slope efficiency obtained was 32% with a threshold pump power of 70 mW.
TL;DR: A novel liquid-level sensor with a high-birefringence-fiber loop mirror (HBFLM) based on a uniform-strength cantilever beam (UCB) is proposed and demonstrated and can be determined via the laser wavelength within the quasi-linear transmission range of the HBFLM filter.
Abstract: A novel liquid-level sensor with a high-birefringence-fiber loop mirror (HBFLM) based on a uniform-strength cantilever beam (UCB) is proposed and demonstrated. Part of the high-birefringence fiber is pasted onto the central surface of the UCB. A hollow suspending pole is utilized to apply force at the end of the beam. The applied force varies with the change of the liquid level, leading to a change of transmission intensity. Thus the variation of liquid level can be determined via the laser wavelength within the quasi-linear transmission range of the HBFLM filter. Its sensitivity, resolution, and linear measurement range reach 0.047/cm, 10 mm, and 140 mm, respectively. The advantages of the sensor include simple structure, high sensitivity, low cost, and good repeatability, etc. The sensing signal can be directly detected by a photodetector and does not require complicated demodulation devices.
11 Sep 2006
TL;DR: It is found that adiabatic variation of polarization of fiber mode enables efficient coupling of a PM fiber supporting linearly polarized modes and a chiral fiber supporting circularly or elliptically polarized modes.
Abstract: Examples of adiabatic modification of optical fiber parameters while maintaining single-mode propagation are discussed in the paper. It is found that adiabatic variation of polarization of fiber mode enables efficient coupling of a PM fiber supporting linearly polarized modes and a chiral fiber supporting circularly or elliptically polarized modes.
TL;DR: In this paper, the first air-core photonic-bandgap fiber gyroscope was demonstrated with a 235m fiber coil, achieving a minimum detectable rotation rate of 2.7deg/h and a long-term stability of 2deg/H.
Abstract: We report the demonstration of the first air-core photonic-bandgap fiber gyroscope. Because the optical mode in the sensing coil travels largely through air, which has much smaller Kerr, Faraday, and thermal constants than silica, far lower dependencies on power, magnetic field, and temperature fluctuations are predicted. With a 235-m fiber coil, we observe a minimum detectable rotation rate of ~2.7deg/h and a long-term stability of ~2deg/h, which are consistent with the Rayleigh backscattering coefficient of the fiber and comparable to that measured with a conventional fiber
TL;DR: Two-photon interference with > 98% visibility and Bellpsilas inequality violation by > 8 standard deviations are observed at 77 K, without subtracting background Raman photons.
Abstract: We study the purity of correlated photon pairs generated in a dispersion-shifted fiber at various temperatures. The ratio of coincidence to accidental-coincidence counts greater than 100 can be obtained as the fiber is cooled to liquid-nitrogen temperature (77 K). We then generate polarization-entangled photon pairs by using a compact counterpropagating scheme. Two-photon interference with visibility >98% and Bell's inequality violation by >8 standard deviations of measurement uncertainty are observed at 77 K, without subtracting the accidental-coincidence counts due to background Raman photons.
TL;DR: By pumping the fiber containing the fabricated FBG, it was possible to realize a fiber laser with an output power of 38 mW, a slope efficiency of 21.1%, and low noise (SNR=60 dB).
Abstract: We report the inscription of fiber Bragg gratings (FBGs) into a nonphotosensitive Er-doped fiber by using a phase-mask scanning technique with near IR femtosecond laser pulses. A grating of 40 mm length with a period of 1.075 μm was realized. We measured transmission losses of −18.9 dB at λ=1554.5 nm with a FWHM bandwidth of 0.15 nm. By pumping the fiber containing the fabricated FBG, it was possible to realize a fiber laser with an output power of 38 mW, a slope efficiency of 21.1%, and low noise (SNR=60 dB).
TL;DR: A novel multiwavelength Brillouin-erbium fiber laser (BEFL) is demonstrated, in which the BrillouIn pump is self-excited within the linear cavity, instead of the injection from the external cavity or direct generation in the intracavity.
Abstract: We have demonstrated a novel multiwavelength Brillouin-erbium fiber laser (BEFL), in which the Brillouin pump is self-excited within the linear cavity, instead of the injection from the external cavity or direct generation in the intracavity. By using this simple scheme, the generation of more than 160 Brillouin Stokes lines has been experimentally demonstrated, which is the largest one achieved in BEFLs to the best of our knowledge. Also, the single longitudinal mode operation and the low noise performance of output wavelength line have been confirmed. Meanwhile, the experiment demonstrates that the BEFL performs good stability on both the operating wavelengths and the output power of each wavelength.
TL;DR: In this article, a method for producing high optical and geometrical quality glass tubes and photonic crystal fiber (PCF) preforms, without using extrusion or drilling at any stage, is presented.
Abstract: We report a method for producing, from the raw materials, high optical and geometrical quality glass tubes and photonic crystal fiber (PCF) preforms, without using extrusion or drilling at any stage. A thermal glass study was carried out in order to choose the appropriate glass composition to avoid crystallization problems during the tube, preform and fiber fabrication. A two period PCF was fabricated in addition to a co-doped Erbium and Thulium photonic crystal fiber. In the latter, a 187 nm wide amplified spontaneous emission (ASE) spectrum was obtained when pumping a 15 cm long fiber at a wavelength of 790 nm.
TL;DR: The optimum signal for use as a frequency reference in a 0.8 m long, 20 microm diameter fiber is found to occur at about 0.5 torr for 30 mW of pump power.
Abstract: Saturated absorption spectroscopy is performed on the acetylene ν1 + ν3 band near 1532 nm inside photonic bandgap fibers of small (~10 μm) and large (~20 μm) core diameters. The observed linewidths are narrower in the 20 μm fiber and vary from 20 to 40 MHz depending on pressure and power. Variations in the background light transmission, attributed by others to surface modes, are significantly reduced in the 20 μm fiber. The optimum signal for use as a frequency reference in a 0.8 m long, 20 μm diameter fiber is found to occur at about 0.5 torr for 30 mW of pump power. The saturation power is found by modeling the propagation and attenuation of light inside the fiber.
TL;DR: In this article, a novel design of a remote sensor for temperature detection based on surface plasmon resonance and optical fiber technology is presented, which theoretically analyzes the performance of proposed sensor under different conditions related to its constituents, i.e., optical fiber, metallic layer, sensing region, and launched light.
TL;DR: In this article, a new type of optical-fiber surface-plasmon-resonance (SPR) sensor based on a thin metallic film and long-period fiber gratings for measuring small changes of refractive index of analyte is presented.
Abstract: A new type of optical-fiber surface-plasmon-resonance (SPR) sensor based on a thin metallic film and long-period fiber gratings for measuring small changes of refractive index of analyte is presented. This sensor simply employs a long-period fiber grating with a proper period to couple a core mode (HE11) to the copropagating cladding mode that can excite a surface-plasmon wave (SPW). The mainly theoretical base used to analyze this new structure is the unconjugated form of coupled-mode equations. In this new SPR sensor, the variation of the refractive index of analyte is determined by monitoring the change of the transmitted core mode power, which is calculated by unconjugated two-mode coupled-mode equations at a fixed wavelength. The numerical results have demonstrated that this new and simple configuration may be used as a highly sensitive amplitude sensor. As far as the excitation of SPW, the model of numerical simulation, and the complexity of measurement equipment are concerned, this new structure is superior to the proposed sensor, consisting of a bent polished single-mode SPR optical fiber. Furthermore, the structure can be easily adapted for a SPR fiber optical probe if a mirror is deposited on the fiber tip.