Precise dispersion measurement is important for various applications, including optical communications, laser cavity design, and nonlinear optics. In this work, we present a dispersion measurement method for the fiber under test inside the Fourier Domain Mode-Locked (FDML) laser by locating the sweet spot regime under the different driving frequencies of the Fabry-Perot tunable filter. The group delay resolution achieved is 2.88 ps, an order of magnitude higher than other dispersion measurement methods based on phase shift or pulse delay. The proposed dispersion measurement method has high resolution and simple configuration, making it promising for measuring the dispersion of special fibers or conventional fibers near their zero-dispersion wavelengths.
Despite more than 40 years of development, it remains difficult for optical logic computing to support more than four operands because the high parallelism of light has not been fully exploited in current methods that are restrained by inefficient optical nonlinearity and redundant input modulation. In this paper, we propose a large-scale optical programmable logic array (PLA) based on parallel spectrum modulation. By fully exploiting the wavelength resource, an eight-input PLA is experimentally demonstrated with 256 wavelength channels. And it is extended to nine-input PLA through the combination of wavelength’s and spatial dimensions. Based on PLA, many advanced logic functions like 8-256 decoder, 4-bit comparator, adder and multiplier, and state machines are first realized in optics. We implement the two-dimensional optical cellular automaton (CA) for what we believe is the first time and run Conway’s Game of Life to simulate the complex evolutionary processes (pulsar explosion, glider gun, and breeder). Other CA models, such as the replicator-like evolution and the nonisotropic evolution to generate the Sierpinski triangle are also demonstrated. Our work significantly alleviates the challenge of scalability in optical logic devices and provides a universal optical computing platform for two-dimensional CA.
We demonstrate the generation of Kerr frequency combs with controllable intracavity soliton states by seeding the single continuous wave (CW) driven two coupled nonlinear microresonators with a pulsed trigger. The stable one-, two-, or three-soliton frequency comb can be realized deterministically simply by adjusting the pulse intensity of the trigger signal. Numerical simulations show that the generation of the mode-locked soliton frequency combs is robust without going through any instability or chaotic states. These results provide a means for the deterministic and controllable generation of optical Kerr frequency combs on integrated chips.
Thin film lithium niobate (LN) is considered a promising platform for integrated photonics owing to its exceptional electro-, nonlinear-, and acousto-optic properties. In this work, we propose the generation of broadband optical frequency combs in an LN microring resonator by dispersion engineering. We design the structure of the LN waveguide to adjust the effective refractive index of its fundamental mode so that the microring resonator can generate two dispersive waves near the pump light to achieve a broadband optical frequency comb up to 4/5-octave range (about 110 THz). The broadband frequency comb is crucial for future on-chip LN nonlinear photonics applications.
This paper presents a novel optical fiber device based on a polymer suspended mirror on the end facet of an optical fiber. With an own-developed optical 3D micro-printing technology, SU-8 suspended-mirror devices (SMDs) were successfully fabricated on the top of a standard single-mode optical fiber. Optical reflection spectra of the fabricated SU- 8 SMDs were measured and compared with theoretical analysis. The proposed technology paves a way towards 3D microengineering of the small end-facet of optical fibers to develop novel fiber-optic sensors.
An alternative light source for coherent anti-Stokes Raman scattering (CARS) microspectroscopy based on red-shifted solitons in a polarization-maintaining photonic crystal fiber (PM-PCF) is experimentally demonstrated. By coupling femtosecond pulses into the anomalous dispersion region of the fundamental mode of a PM-PCF along the slow and fast axes, the red-shifted solitons generated can be used as the Stokes beams when the pump pulses are chosen as the pump beams. Through the process of red-shift, the frequency differences of the pump-Stokes beams are tunable in the ranges of 0 to 4068 cm−1 and 0 to 4594 cm−1, respectively. Moreover, because of the well maintained polarization states of the pump and Stokes beams and the high output powers of the solitons, CARS microspectroscopy using the proposed source will have a high signal-to-noise ratio and short data acquisition time. CARS microspectroscopy based on the proposed all-fiber light source can be used for studying a wide range of vibrational Raman spectra.
Non-adiabatic pulse compression of cascaded higher-order optical soliton is investigated. We demonstrate high degree
compression of pulses with soliton order N=2, 3, 4 and 5 in two or three nonlinear fibers with different second-order
dispersion coefficients. Each fiber length is shorter than half of its soliton period. This compression technique has
significant advantages over the widely reported adiabatic and higher-order soliton compression.
We proposed and demonstrated a novel, simple, and low cost method for all-optical clock recovery based on the switching between two injection-locked longitudinal modes in a dc-biased multi-quantum-well Fabry-Perot laser diode (FP-LD). The dc biased FP-LD is simultaneously injection-locked by a return-to-zero data signal at one of the longitudinal modes of the FP-LD and self-seeded at another longitudinal mode by using a uniform fiber Bragg grating as a feedback component. The powers and detunes of the data signal and self-seeding signal are chosen such that self-seeding is realized in the FP-LD only when data signal power is low. Clock signals of data streams at different data rates can be obtained by tuning the optical delay line in the external self-seeding loop. We have demonstrated all-optical clock recovery at 10 GHz. The pulse width, time-bandwidth product, side mode suppression ration, root mean square timing jitter, and average power of the recovered clock signals are 50 ps, 0.5, 50 dB, 248 fs, and 3.6 dBm, respectively. Clock recovery is possible at wavelength within the gain band of the FP-LD. We also find and explore in the experiment the influence of detune between the external data signal and the nearest FP-LD longitudinal mode to the recovered clock.
We develop a simple iterative model to simulate a laser with homogeneous gain and intensity dependent loss. Simulation
results show that a laser with homogenous gain can operate at multiple wavelengths if the intensity-dependent loss
exhibits saturable transmitter characteristics. Our results also show that for nonlinear losses that have both saturable
transmitter and saturable absorber characteristics, such as arises from nonlinear optical loss mirrors (NOLM) or
nonlinear polarization rotation (NPR), the multiwavelength output power spectrum can become very flat. The laser can
also exhibit periodic and chaotic behaviors. We find that the same theoretical model can also be used to describe multipulsing
dynamics of mode-locked lasers when the cavity energy increases. Near the multi-pulsing transitions, both
periodic and chaotic behavior can be observed as operating states of the laser cavity. Our iterative model provides a
simple geometrical description of the entire multi-pulsing transition behavior as a function of increasing cavity energy.
The model captures all the key features observed in experiments, including the periodic and chaotic mode-locking
regions, and further provides valuable insight into laser cavity engineering for maximizing performance.
A room-temperature multiwavelength erbium-doped fiber laser (EDFL) based on a nonlinear high-birefringence fiber loop mirror (HiBi-FLM) is proposed and demonstrated. The nonlinear HiBi-FLM can induce not only wavelength-dependent loss (WDL) but also intensity-dependent loss (IDL). WDL and IDL can effectively suppress the mode competition caused by homogeneous gain broadening of the erbium-doped fiber (EDF), and ensure stable and uniform power distribution over wavelengths. As a result, up to 50-wavelength lasing operations with wavelength spacing of 0.8 nm, and more than 100-wavelength operations with wavelength spacing of 0.14 nm are achieved. The power distribution over the wavelengths is uniform, and the power fluctuation in each wavelength is smaller than 0.2 dB.
A novel and simple method is presented to generate a tunable high-repetition-rate pulse train based on dual-mode self-injection locking of a Fabry-Perot laser diode (FP-LD). Two fiber Bragg gratings (FBGs) are used in the experiment as feedback components. The two self-injection-locked modes evolve into a high-power, high-repetition-rate pulse train through the interplay between self-phase modulation and anomalous dispersion in a highly nonlinear fiber. A 139.6-GHz transform-limited pulse train with a peak power of 120 mW is generated. The pulsewidth is 1.7 ps, and the time-bandwidth product is 0.31. The repetition rate can be tuned by tuning the Bragg wavelengths of one of the two or both FBGs to coincide with other FP-LD modes. The output pulse is stable.
We experimentally demonstrate a high pressure sensor based on a polarization-maintaining photonic crystal fiber (PMPCF)
with Sagnac loop configuration for downhole application. The pressure sensitivity of the proposed sensor is 4.21
nm/MPa and 3.27 nm/MPa at ~1320 nm and ~1550 nm respectively. High pressure measurement up to 20 MPa has been
achieved in our experiment. The sensor also shows reduced temperature sensitivity, making it an ideal candidate for
pressure sensing in harsh environment.
A wavelength switchable multiwavelength actively mode-locked fiber-ring laser based on highly nonlinear photonic crystal fiber (PCF) and polarization-dependent mode coupling to multimode-fiber Bragg grating (MMFBG) is proposed. Twenty meters of highly nonlinear dispersion-shifted PCF (DS-PCF) is inserted into the fiber ring cavity to suppress gain competition through the four-wave-mixing (FWM) effect. A mode scrambler is attached to the multimode fiber (MMF) to introduce a polarization-dependent mode coupling to the MMFBG. Through changing polarization in the cavity, stable and switchable one-wavelength, two-wavelength (wavelength spacing of 0.8 and 2.4 nm), and three-wavelength simultaneously actively mode-locked optical pulse trains at a repetition rate of 5 GHz are obtained. We show that high nonlinearity introduced by the nonlinear PCF in the cavity can improve significantly supermode suppression ratio (SMSR) of the multiwavelength pulses generated and a sidemode suppression ratio (SMSR) of 58 dB is realized.
Transmission of eight channel 100Gbit/s CS-RZ DQPSK signals up to 1500km SSMF was demonstrated. This
transmission system only used EDFA and did not adopt coherent detection and polarization multiplexing. The span
spacing in this system varies from 80km to 100km to simulate the practical optical network.
Keywords: Transmission system, modulation format
We demonstrate dispersion monitoring of differential phase-shift keying (DPSK) modulated optical transmission system
by measuring RF components of detected optical signal. The results show that this scheme can realize dispersion
monitoring up to 4320ps/nm and sensitivity up to 15.5(ps/nm)/dBm. The effect of OSNR on the performance of the
monitoring system are studied and discussed.
We proposed and demonstrated the application of a polarization-maintaining photonic crystal fiber for torsion sensing.
The sensor has high twist angle resolution and exhibits reduced temperature sensitivity, making it an ideal candidate for
torsion sensing.
KEYWORDS: Switches, Signal processing, Packet switching, Modulation, Signal generators, Semiconductor lasers, Switching, Fabry–Perot interferometers, Process control, Optical signal processing
We will describe recent results in all-optical packet switching with all-optical header processing using Fabry-Perot laser diodes (FP-LD). First, we will report an all-optical header processor and control signal generator using a single FP-LD with a special two-intensity-level control signal and a novel self-routing address format for the data packets. We then show that the special control signal can be generated by direct modulation of a DFB laser with square electrical pulses thus simplifying implementation. We will demonstrate that a single Fabry-Perot laser diode can also serve as an all-optical on/off switch with all-optical header processing. The header rate is 5 Gb/s and the payload rate is 10 Gb/s. The all-optical on/off switch can also be realized by using a FP-LD as the header processor only and executing the packet switching at a separate stage. The two-stage implementation of all-optical on/off switch eliminates the residue header bits problems if only a single FP-LD is used. Finally, we propose an all-optical packet-switched ring network which can be constructed from the all-optical on/off switches demonstrated.
Recent developments of Bismuth-based erbium-doped fibers (Bi-EDFs) have demonstrated their potential applications for broadband amplifiers, particularly for the L-band in DWDM systems, for short pulse amplifiers to be used in very high bit-rate transmission systems (up to 160 Gbps), and for ultra wideband tunable fiber ring lasers. The low concentration quenching of erbium ions in Bi-based glass permits efficient high erbium concentration Bi-EDFs (up to 26,000 ppm) to be fabricated allowing the realization of ultra-short length erbium-doped fibre amplifiers and fiber lasers. In this paper, we reported the performance of two Bi-EDFs with different erbium ions concentrations for signal amplification. One fiber was doped with 6,470 wt-ppm of erbium ions and the other was doped with 3,250 wt-ppm of erbium ions. The performance of a 253-cm long Lanthanum co-doped Bi-based EDF (3,250 ppm of erbium) for the amplification of 142 wavelength channels was evaluated. 140 of the input signals were located at the 50-GHz ITU grid. Signal gains of over 20 dB and NF less than 6.7 dB were measured for all the channels with wavelengths ranging from 1554.13 nm to 1612.22 nm (i.e. over 58 nm). 3-dB bandwidth of 53.9 nm and quantum conversion efficiency of about 60 % were attained when the fiber was pumped with 350 mW and 623 mW of pump power, respectively. The performance of an ultra-short length Bi-EDFA, using 23-cm of Bi-EDF doped with 6,500 ppm of erbium ions pumped at 980 nm, for the amplification of picosecond pulses will be discussed. The results of an ultra wideband (106 nm) tunable fiber ring laser based on the higher erbium concentration Bi-EDF will also be presented.
We report a multi-wavelength fiber laser with a semiconductor optical amplifier. The lasing wavelength of the laser can be adjusted from 1590 nm to 1645 nm by adjusting the round-trip cavity loss.
A microprocessor controlled feedback system using a linear variable differential transformer to measure the compression of a fiber Bragg grating with a view to improve the tuning accuracy of a fiber grating laser is reported. This technique overcomes the large hysteresis of the PZT actuator normally used to compress the grating. A tuning range of about 20 nm with a readout wavelength accuracy of better than +/- 0.05 nm was achieved.
Spectral broadening of single-frequency laser pulses by optical cross-phase modulation (XPM) with chaotic laser pulses in birefringent single-mode optical fibers is investigated numerically and results are compared with experiments. By this process we have generated laser pulses of variable bandwidth (1 - 25 angstrom) at the fundamental wavelength (1053 nm) for amplification in high power solid-state Nd:glass lasers used for inertial confinement fusion research. Simulations indicate that a temporally smooth XPM pulse can be generated with intensity fluctuations of less than 10% and spectral width greater than 50 angstrom using a short length (approximately 5 m) of special low dispersion and low birefringence fiber, e.g., D equals 10 ps/nm-km (normal dispersion) and (Delta) n equals 2 X 10-5. Readily available fibers of similar length, with parameters of D equals 40 ps/nm-km and (Delta) n equals 6 X 10-5, can give spectral widths exceeding 25 angstroms, but the noise will range from 25 to 60%. Broadband laser pulses generated by XPM are now routinely used at Lawrence Livermore National Laboratory for active smoothing of the laser irradiance on targets by the technique of smoothing-by-spectral dispersion.
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