Statistical dispersion budgeting method for single-mode fibertransmission systems

A statistical dispersion budgeting method for spliced single-mode fiber transmission spans is proposed. The method aids in the design of fiber spans in high bit-rate (>1 Gb/s) systems. Intended for spans containing many splices, the method yields, in theory, greater span lengths than those calculated with the traditional worst-case dispersion budgeting method     

Investigation of polarization dispersion in long lengths of single-mode fiber using multilongitudinal mode lasers

We have used multilongitudinal mode lasers to investigate the polarization properties of long lengths of single-mode fiber cable. We find that the individual longitudinal modes are >99-percent polarized after propagation through 54.6 km of cabled fiber; however, the different longitudinal modes have different states of polarization at the output. This difference is caused by polarization dispersion, and we estimate a propagation delay difference for the two principal states of polarization to be 0.42 ps in the 54.6 km of cabled fiber.     

Soliton technique to characterize single-mode fiber dispersion

Transmitting subpicosecond pulses at moderate powers over a few meters of fiber creates a notch in the pulses' power spectra in the vicinity of the fiber's zero-dispersion wavelength. This is caused by the interaction of nonlinear self-phase modulation and third-order dispersion. This phenomenon can be used to determine the zero-dispersion wavelength of single-mode fibers     

Estimation of single-mode waveguide dispersion using an equivalent-step-index approach

In the letter, the feasibility of applying the equivalent-step-index parameters to estimate the single-mode waveguide dispersion of various radially inhomogeneous profiles is studied. The results are compared to the actual values obtained by numerical techniques and the errors estimated. The equivalent-step approach seems to be accurate only for cases where the profiles do not deviate severely from the step-index profile.     

Millimeter wave narrowband optical fiber links using externalcavity semiconductor lasers

We present the theoretical analysis and the experimental implementation of a narrowband millimeter wave optical fiber communication system using an external cavity semiconductor laser. We derive analytic expressions and present experimental data for the modulation response, relative intensity noise, carrier-to-noise ratio, and harmonic distortion for a semiconductor laser in an external cavity operating as a transmitter in the millimeter wave frequency range. We present a system implementation of this capable of transmitting 40-Mbt/s digital data at a 35-GHz subcarrier frequency with bit-error rates below 10^-9 over a 6.3-km-long optical fiber link     

Dynamical noise in single-mode distributed feedback fiber lasers

The dynamics of erbium distributed feedback fiber lasers close to steady state is analyzed taking into account spatial hole burning and the nonuniform modefield distribution. A set of linearized equations is derived and used to obtain theoretical amplitude and frequency noise spectra for spontaneous emission noise and generic pump power noise. Analytic formula for important laser characteristics including pump slope efficiency and relaxation oscillation frequency are also obtained. It is found that the spatial distribution of the laser mode plays and important role in determining the output characteristics of the laser.     

Noise properties of stabilized single-mode lasers in fiber interferometers

A compact fiber interferometer is used to stabilize the frequency fluctuations of GaAlAs laser. The properties of the laser are determined before and after stabilization. The application of this technique to conventional interferometer demodulation schemes is discussed.     

Multiquantum-well lasers with tapered active stripe for direct coupling to single-mode fiber

We demonstrate narrow beam divergence in 1.3-/spl mu/m wavelength multiquantum-well (MQW) lasers with an active stripe horizontally tapered over the whole cavity, for direct coupling to single mode-fibers. The lasers have reduced output beam divergence in a simple structure which does not contain an additional spot-size transformer. The fabricated laser shows narrow beam divergence of /spl sim/12/spl deg/, while a low-threshold current of 6.9 mA and a high efficiency of 0.62 mW/mA are realized. Furthermore, a direct-coupling efficiency to a single-mode fiber is -4.0-dB and -3-dB alignment tolerance is /spl plusmn/2.5 /spl mu/m.     

Chromatic dispersion measurements over a 50-km single-mode fiber

Chromatic dispersion has been measured over a 50-km-long single-mode fiber, using five sinusoidally modulated laser diodes. Results indicate that chromatic dispersion characteristics for single-mode fibers with 33-dB optical loss can be evaluated in the1.2-1.6-mum spectral region.     

Technique for direct measurement of single-mode fiber chromatic dispersion

A technique for the direct measurement of single-mode fiber chromatic dispersion is presented. The technique uses wavelength modulation to provide a differential fiber chromatic delay signal from which chromatic dispersion is obtained directly. The system is described in detail and practical measurement results shown to illustrate the high accuracy of the technique and its versatility in use with all fiber types.     

A single-mode fiber with chromatic dispersion varying along thelength

A method for fabrication of a novel type of optical fiber with dispersion varying along the fiber length is described. The method takes into account the calculated dependence of fiber dispersion on fiber core diameter for the measured profile of the preform and the desirable dispersion dependence on the fiber length. The main optical parameters of the drawn fiber are theoretically studied and experimentally measured. The fibers are of great interest for nonlinear fiber optics. Such applications of the fibers, such as high-quality soliton pulse compression, soliton pulsewidth stabilization through compensation of losses, and generation of a high-repetition-rate train of practically uninteracting solitons, are considered     

Distributed single-mode fiber to single-mode planar waveguidecoupler

Light transfer between a curved single-mode fiber and a single-mode planar waveguide is investigated experimentally in dependence on the refractive index and thickness of the planar waveguide and for different polishing depths. Marcuse's model is applied to treat theoretically the coupler, leading to a very good agreement with the experimental results     

23-GHz and 123-GHz soliton pulse generation using two CW lasers andstandard single-mode fiber

Theoretical and experimental results for 23-GHz and 123-GHz near-transform-limited soliton pulse generation at 1.55 μm is presented. The technique uses soliton compression of the beat signal between two CW lasers in standard commercially available single-mode optical fiber and does not require longitudinal variation of the fiber dispersion     

Laser to single-mode fiber assembly using an electroforming technique

One of the most difficult problems in coupling laser diodes to single-mode fibers is maintaining alignment while the two components are locked into place. The authors report a novel approach to the lockup process that uses electroforming. This technique solves the isolation and train relief problem by locking the laser and fiber into a single structure rather than by mounting both to a common base. With this novel technique and simple butt coupling, coupling efficiencies as high as 14% have been achieved with very little alignment shift during lockup. The completed structure is at least 100 times smaller in volume than conventional packages and provides strain relief and isolation from mechanical disturbances.<>     

Comments on "Dynamical noise in single-mode distributed feedback fiber lasers"

The comments given here refer to the two excellent and complete papers by Foster (see ibid., vol.40, no.7, p.884, 2004 and ibid., vol.40, no.9, p.1283, 2004). After closely studying the papers, we have found a couple of issues that require comments in order to understand and use the model. Despite this, one should honor the achievements in the papers in which Foster establishes an accurate analytical model for a DFB fiber laser. The comments relate to a gain parameter and the noise arising from pump power fluctuations and something that affects the noise equations, which we believe to be a small misprint.     

Field to dispersion relationships in single-mode fibres

Exact explicit expressions are obtained which relate (i) the modal spotsize and (ii) the core power to the dispersion parameters in single-mode optical fibres. Spotsize can therefore be expressed exactly in terms of the core power, with the degree of guidance playing a crucial role in the relationship.     

Statistical distribution of polarization-dependent loss in thepresence of polarization-mode dispersion in single-mode fibers

The statistical distribution of polarization-dependent loss in single-mode fibers is studied via Monte-Carlo simulations. In the presence of polarization-mode dispersion, it is found that the probability density function of polarization-dependent loss is a combination of Rayleigh and Maxwell distributions     

Statistical analysis on stimulated Raman crosstalk in dispersion-managed fiber links

Power impairments due to stimulated Raman scattering (SRS) in dispersion-managed (DM) fiber links are evaluated theoretically. We extend previous work on the statistical analysis of SRS crosstalk to the case of multiple fiber segments. Closed-form formulas are derived, and the applicable range is presented by comparison with simulation results. The SRS crosstalk in DM fiber links is evaluated using derived formulas, and the preferable configuration of DM fiber links for suppressing SRS crosstalk is discussed. We also evaluate the exact power penalty induced by the SRS crosstalk in consideration of the log-normal waveform distribution due to SRS and non-Gaussian noise and clarify the system bounds in some typical DM fiber links. The developed approach provides a design rule for DM fiber links from the viewpoint of SRS crosstalk suppression.     

Cross-phase modulation in fiber links with multiple opticalamplifiers and dispersion compensators

We have theoretically and experimentally investigated the cross-phase modulation (XPM) effect in optical fiber links with multiple optical amplifiers and dispersion compensators. Our theory suggests that the XPM effect can be modeled as a phase modulator with inputs from the intensity of copropagating waves. The frequency response of the phase modulator corresponding to each copropagating wave depends on fiber dispersion, wavelength separation, and fiber length. The total XPM-induced phase shift is the integral of the phase shift contributions from all frequency components of copropagating waves. In nondispersive fibers, XPM is frequency-independent; in dispersive fibers, XPM's frequency response is approximately inversely proportional to the product of frequency, fiber dispersion, and wavelength separation. In an N-segment amplified link, the frequency response of XPM is increased N-fold, but only in very narrow frequency bands. In most other frequency bands, the amount of increase is limited and almost independent of N. However, in an N-segment amplified link with dispersion compensators, the frequency response of XPM is increased N-fold at all frequencies if the dispersion is compensated for within each fiber segment. Thus, the XPM-induced phase shift is smaller in systems employing lumped dispersion compensation than in systems employing distributed dispersion compensation     

A broad-band superfluorescent fiber laser using single-mode dopedsilica fiber combinations

We demonstrate the possibility of broadening the emissions spectra of superfluorescent fiber lasers by combinations of different kinds of single-mode doped silica fibers. We obtained an optical bandwidth of more than 70 nm (FWHM) between 1030 and 1100 nm using Nd:Cs, Nd:Ge, and Yb-doped fibers. The total output power measured from the single-mode fibers was more than 100 μW in a single pass configuration