Showing papers on "Polarization mode dispersion published in 1992"

Automated measurement of polarization mode dispersion using Jones matrix eigenanalysis

Abstract: Polarization mode dispersion (PMD), which can limit the bandwidth of optical transmission links, has been difficult to measure in a manner independent of human judgment, leading to difficulties in automating the measurement. It is shown that PMD in any linear, time-invariant network can be completely characterized by eigenanalysis of Jones matrices measured at a series of discrete wavelengths, even for networks exhibiting polarization-dependent loss. A fast, automated system using a tunable laser and an accurate, real-time polarimeter affords the temporal accuracy of approximately 2% down to a limit of several femtoseconds, as demonstrated by comparison with other techniques and comparison with known samples. Both the principal states of polarization and the group delay difference were measured as a function of optical frequency. >

Dispersion compensating devices and systems

Abstract: Disclosed is a family of dispersion compensating optical fibers that are adapted for use with conventional single-mode transmission fibers that are optimized for zero dispersion operation at a wavelength in the range from 1290 nm to 1330 nm to form a transmission link suitable for low dispersion operation in the 1520-1565 nm wavelength window. The dispersion compensating fibers are capable of providing a dispersion more negative than -20 ps/nm-km and attenuation less than 1 dB/km at wavelengths in the 1520-1565 nm region. Certain of the dispersion compensating fibers also exhibit a dispersion versus wavelength relationship having a negative slope in the 1520-1565 nm region, to compensate for the dispersion versus wavelength slope of the transmission fiber. The dispersion compensating fiber can be advantageously combined with a fiber amplifier to form a compensator that is adapted to overcome attenuation introduced into the system by the dispersion compensating fiber. In one embodiment, the dispersion compensating fiber is also a distributed fiber amplifier.

Broadband dispersion compensation by using the higher-order spatial mode in a two-mode fiber

Abstract: A fiber-optic technique for compensating both first- and second-order group-velocity dispersion in single-mode fiber spans is demonstrated by using the large waveguide dispersion that occurs for the higher-order (LP11) spatial mode in a two-mode fiber near cutoff. Complete restoration of 7-ps pulses that had been dispersed by a factor of 10 in 5 km of single-mode fiber is demonstrated over a 20-nm-wavelength window. First-order dispersion as large as −228 ps/(nm km) is observed for the LP11 mode at 1560 nm in the two-mode fiber.

Time evolution of polarization mode dispersion in long terrestrial links

Abstract: Although polarization mode dispersion is well characterized in terms of principal states of polarization (PSP) and of their differential group delay (DGD), both analytically and experimentally, very few data have been published on their time evolution in terrestrial links, where temperature fluctuations are larger than in undersea links. The authors demonstrate strong correlation between temperature fluctuations and evolution of DGD and PSP. Correlation is even stronger in links which include connectors. Also, they report that DGD, as a random function of time, has a Maxwellian distribution and thus shows that it is an ergodic process. >

Method and apparatus for measuring polarization mode dispersion in optical devices

Abstract: An instrument includes a polarized optical source for producing three sequential predetermined states of polarization of a light beam at each of at least two wavelengths, as well as an optical polarization meter for measuring the polarization of a portion of the light beam at each wavelength transmitted by or reflected from an optical network by splitting it into four beams, passing three of the beams through optical elements, measuring the transmitted intensity of all four beams, and calculating Stokes parameters. The three sequential predetermined states of polarization at each wavelength yield three corresponding Jones input vectors at each wavelength, and the Stokes parameters for the responses of the optical network are converted to three Jones output vectors at each wavelength. A Jones matrix for the optical network to within a complex constant is then computed from the Jones input and output vectors at each wavelength. Polarization mode dispersion in the optical network is determined from these matrices.

Optical equalization of polarization dispersion

Abstract: In this paper, we describe a demonstration of the optical equalization of polarization dispersion in direct-detection lightwave systems. We use a polarization controller to adjust the polarization into a fiber to one of the principal states of polarization of the fiber, which eliminates first-order polarization dispersion. Results for a 2.5 Gbps, externally modulated system with a fiber with 120 ps rms of polarization dispersion, show that by using the equalizer we maintain a 10-9 BER, while without the technique the BER varies with time from 10-5 to 10-9. At 10 Gbps, the equalizer allows reliable bit detection even though the eye is closed without equalization, demonstrating an order of magnitude increase in the dispersion-limited B2L product, in agreement with our analytical and computer simulation results. We also describe a demonstration of the technique at the receiver, and show how to implement an adaptive polarization controller to continuously track the principal states using a gradient search algorithm. This technique provides bit-rate-independent equalization of first-order polarization dispersion.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Pressure dependence of polarization mode dispersion in HiBi fibers

Abstract: Pressure effects in polarization maintaining fibers are investigated both experimentally and theoretically. Interferometric measurements of the propagation times and polarization mode dispersion as a function of hydrostatic pressure over the range 0 to 40 MPa are presented. The finite-element method is used to calculate the pressure-induced variations of the asymmetrical stress in the core. It is observed and comprehensively explained that the birefringence increases with external applied hydrostatic pressure. >

Soliton instabilities from resonant random mode coupling in birefringent optical fibers.

Abstract: We study soliton propagation in birefringent fibers with resonant random mode coupling. We determine the stability boundary for the critical value of polarization mode dispersion as a function of the finite correlation distance of the random polarization coupling.

Random birefringence and polarization dispersion in long single – mode optical fibers

Abstract: Non-ideal single-mode fibers are affected by birefringence and coupling, which cause polarization dispersion. They are conveniently modeled in terms of the so-called principal states of polarization and of their differential group delay. We review this formalism and its application to the evolution of polarization along a randomly varying fiber, and to concatenation of group delays over long links consisting of N spliced fibers.

Optical isolator with polarization dispersion correction

Abstract: An optical isolator is disclosed which includes means for correcting the polarization dispersion present in conventional polarization independent optical isolators. Correction of the polarization dispersion is provided by a birefringent plate of length l, the length chosen to equalize the optical signal path traversed by each polarization state (i.e., e-rays and o-rays) through the complete isolator.

Interferometric loop method for polarization dispersion measurements

Abstract: A novel method for polarization dispersion measurements using an interferometric loop is presented. It can be achieved using a particularly simple setup and provides a representation of the probability distribution of the polarization dispersion.

Concatenation of polarization dispersion in single-mode fibers: A monte-carlo simulation

Abstract: We present a model for non-ideal long single-mode fiber links affected by polarization mode dispersion. It leads to simple expressions for the overall polarization delay and for the r.m.s. width of the impulse response, which entail systematic simulation on personal computers within reasonable CPU times. Simulations show that the mean differential group delay and the double r.m.s. width of the impulse response coincide in such a way that both quantities can characterize the fiber polarization mode dispersion. In particular, both grow as the square root of the link length when the correlation length of the perturbation is much smaller then the fiber length. This confirms the results obtained by other authors under restrictive approximations.

Soliton technique to characterize single-mode fiber dispersion

Abstract: 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. >

Experimental investigation of single-mode single-polarization optical fiber.

Abstract: An experimental study of the polarization properties of single-mode optical fibers of differential polarization-mode attenuation is presented. The output state of polarization was measured at various input polarization orientations and wavelengths. The transition from a two-polarization to a single-polarization regime of operation was investigated. Also, the sensitivity to axial strain was studied at the different wavelengths. The polarization dispersion of the fiber was assessed by measuring the visibility of the polarization interference fringes. Experimental results confirm a previous theoretical study based on Muller–Stokes matrix formalism. The experiments carried out suggest useful applications of such fibers for the development of polarimetric sensors.

Spectral Determination of Modal Birefringence and Polarization Dispersion of Polarization-Maintaining Fibers with a high Accuracy

Abstract: This paper describes an experimental set-up allowing the beatlength, the modal birefringence and the polarization dispersion to be measured in a simple way. The measurement procedure is a combination of pressing method and wavelength scanning (WLS) method. The outstanding feature of the measurement device is its very high accuracy. The measurements can be performed in a short time, the experimental set-up being not complicated. All parameters mentioned above can be determined spectrally.

0.78-μm digital transmission characteristics using 1.3-μm optimized single-mode fiber for a subscriber loop

Abstract: The transmission characteristics of digital systems comprised of 1.3-μm zero dispersion, single-mode fibers (1.3-μm SMF) and 0.78-μm band laser diodes (LD) are investigated. The problems encountered in such systems are the degradation of the transmission bandwidth due to the modal noise and the dispersion. This paper describes the transmission-distance limitations due to the mode dispersion and the range of suitability of short wavelength sources in conjunction with the 1.3-μm SMFs is clarified. It is shown from the measurement of the long-term bit-error rate that the self-pulsation LDs are useful. It is shown also that the bandwidth-distance product is limited to 111 MHz km due to the maximum delay difference of 3 ns/km between LP01 and LP11 modes of 1.3-μm SMFs fabricated by the VAD method. Finally, the selection rules of the optical sources are described taking into account the degradations due to the modal noise.

Recent Progress in Polarization Measurement Techniques

Abstract: optical, fiber optics, photonic subsystems, incoherent, photonics, lightwave components New optical polarization measurement techniques are touched upon. An accurate, real-time, fiber-based polarimeter is briefly described, along with its impact on measurement techniques. The capabilities of the polarimeter are dramatically augmented by the addition of a simple polarization synthesizer. The synthesizer allows stimulus-response measurement of devices and networks, allowing calculation of Jones matrices and complete characterization of linear, timeinvariant networks. This capability, along with automated operation and fiber connectors, can make polarization measurements comparable to microwave measurements in their levels of convenience, flexibility, speed and sophistication of analysis. New techniques are presented for measurement of polarization-dependent loss and polarization mode dispersion.

Polarization mode dispersion effects on phase and polarization diversity receivers

Abstract: The objective of this paper is to examine the combined effects of weak phase noise and polarization mode dispersion (PMD) on a coherent receiver employing phase and polarization diversity reception. The receiver is assumed to be subjected to the following: transmitter and receiver polarization misalignment relative to the principal states of the optical fiber, phase noise, polarization mode dispersion, and shot noise. The receiver outputs are investigated for ASK demodulation using square-law and envelope detection. The results show that for the assumed receiver configuration, square law detection provides an output which is independent of PMD, phase noise, and polarization misalignment. Envelope detection results in a receiver output which is dependent on all of these parameters. Furthermore, when phase noise and PMD are simultaneously present, the resulting probability of bit error is no greater than the probability of bit error under worst-case operating conditions when polarization mode dispersion and phase noise are absent.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.