Colorless coherent receiver using 3x3 coupler hybrids and single-ended detection.

We demonstrate a single-ended colorless coherent receiver using symmetric 3x3 couplers for optical hybrids. We show that the receiver can achieve colorless reception of fifty-five 112-Gb/s polarization-division-multiplexed quadrature-phase-shift-keyed (PDM-QPSK) channels with less than 1-dB penalty in the back-to-back operation. The receiver also works well in a long-haul wavelength-division-multiplexed (WDM) transmission system over 2560-km TrueWave® REACH fiber.

Effects of spin process on birefringence strength of single-mode fibers.

Spin process is the most effective and diffused way to reduce polarization mode dispersion in single-mode optical fibers. All theoretical models adopted so far to describe spun fibers assume that the only effect of spin is to rotate fiber birefringence, without affecting its strength. Yet, experimental analyses of this hypothesis are controversial. In this paper, we report on an extensive experimental characterization of birefringence in spun and unspun fibers. Results indicate that the spinning process has no instantaneous effect on birefringence strength, regardless of the kind of fiber; nevertheless, there might be a small average effect on G.652 fibers.

Limits of applicability of polarization sensitive reflectometry.

We present a detailed theoretical analysis of the measurement limits of polarization sensitive reflectometry, imposed by spatial resolution and measurement accuracy. The limits are conveniently represented in a map of constraints. We also describe and experimentally verify a procedure that allows to measure spin profiles of single-mode fibers with spin rates exceeding the measurable range of the reflectometer. The technique consists in twisting the fiber to locally unwind the spin.

Measured phase and group birefringence in elliptical core fibers with systematically varied ellipticities.

This paper presents the first systematic phase and group birefringence measurements of elliptical core fibers covering an unprecedented ellipticity range from 0.1 to 0.9. Experimental results at 1550 nm are compared with simulations, and the birefringence ratio is shown to depend on both ellipticity and core area. Also the dispersion of the group birefringence is discussed.

Distributed characterization of bending effects on the birefringence of single-mode optical fibers.

The effects of bending on randomly birefringent, single-mode optical fibers have been analyzed by means of polarization-sensitive optical frequency domain reflectometry. This distributed, pointwise characterization has been performed on ad hoc drawn spun fibers and on a ribbon cable. Experimental results are in agreement with the theoretical predictions and confirm the effectiveness of reflectometry as a means to characterize polarization properties of optical fibers.