Low Polarization Dependent Loss Research Articles

Polarisation-insensitive semiconductor optical amplifier gate switch with butt-jointed spot-size convertors – its uniformity

A spot-size converted polarisation-insensitive semiconductor optical amplifier gate switch (SS-SOAG) for hybrid integration on a silica-based planer lightwave circuit (PLC) platform has been fabricated and investigated. As a result, a SS-SOAG has been realised with low polarisation-dependent loss and low coupling loss. This device operates over a wavelength range of more than 50 nm, which suggests that it can be applied to various switching components in wavelength routing switching systems. High speed gate operation has also been demonstrated. Fabrication tolerances of the mesa width and the layer thickness have been investigated at a submicron scale to ensure low polarisation dependence and efficient coupling properties. Structural uniformity in a wafer was accomplished using the proposed fabrication technique, which leads to characteristic uniformity of an eight-channel SS-SOAG array.

1 × N fibre coupler employing diffractive optical element

A new broadband 1/spl times/N fibre coupler has been developed which employs diffractive optical elements (DOEs). The fibre coupler consists of an input fibre collimator, two aspherical lenses, a specially designed DOE and arrayed output fibres. The demonstrated 1/spl times/8 fibre coupler has a low polarisation dependent loss of /spl les/0.05 dB an excess loss of /spl les/2.4 dB, and good uniformity of /spl plusmn/0.25 dB over a broad wavelength range of 1510-1570 nm.

Fluorinated polyimide waveguides with low polarization-dependent loss and their applications to thermooptic switches

Fluorinated polyimide waveguides with low polarization dependent loss (PDL) and thermooptic (TO) switches made from them were demonstrated. The waveguides showed loss of less than 0.3 dB/cm at the wavelength of 1.3 /spl mu/m and 0.6 dB/cm at 1.55 /spl mu/m for both TE and TM polarizations. The PDL's were less than 0.1 dB/cm. Extinction ratios of Y-branching-type TO switches fabricated from these waveguides were larger than 20 dB when over 160 mW of electric power was applied at 1.3 /spl mu/m, and over 150 mW at 1.55 /spl mu/m. The switching speed was faster than 8 ms.

Polarization independent, linear-tuned interference filter with constant transmission characteristics over 1530-1570-nm tuning range

We present a polarization independent optical tunable filter (OTF) with nearly constant transmission characteristics over 1530-1570 nm. The tuning is achieved by horizontally sliding an interference filter, resulting in a very low polarization dependent loss (PDL)<0.1 dB and nearly constant characteristics over the tuning range. By cascading interference filters in double or triple stage, narrower bandwidth characteristics are obtained allowing for smaller channel spacing in wavelength division multiplexing (WDM) systems. Experimental results for PDL, loss, and bandwidth are presented and compared to those of angle-tuned filter. The proposed OTF has shown superior performance promising a practical solution for dense WDM applications.

Polarization and wavelength insensitive MQW electroabsorption optical gates for WDM switching systems

We propose using MQW electroabsorption (EA) modulators as optical gates in wavelength-division-multiplexing (WDM) switching systems. A fabricated MQW-EA gate with integrated waveguides showed a high extinction ratio (>30 dB), a low polarization-dependent loss (0.3 dB), and a low wavelength-dependent loss (1.1 dB) within the gain band (1545-1560 nm) of erbium doped fiber amplifiers (EDFAs). Ultra-high-speed (<40 ps) switching of a WDM signal was demonstrated.

Polarization dependent loss in a Ti:LiNbO3 polarization scrambler/controller

We have investigated the polarization dependent loss (PDL) of a waveguide-type polarization scrambler/controller consisting of a half-wave plate (HWP) and a quarter-wave plate (QWP) in series fabricated in x-cut/z-propagating Ti-diffused LiNbO/sub 3/ optical waveguides. Based on the polarization dependences of both the propagation loss coefficient and mode-mismatch loss with fiber at 1.55 /spl mu/m combined with a numerical analysis, the PDL of the fabricated device is estimated to be 0.063 dB. It is shown that the low PDL is a direct consequence of a special anisotropy relation between the propagation loss and waveguide-fiber mode-mismatch loss.

Low polarisation dependence (&lt; 0.3 dB) in an EA modulator using a polyimide-buried high-mesa ridge structure with an InGaAsP bulk absorption layer

The electroabsorption modulator combining a polyimide-buried high-mesa ridge structure with an InGaAsP bulk absorption layer which the authors have developed demonstrates an extremely low polarisation-dependent loss of less than 0.3 dB with a practical and sufficient attenuation of 20 dB.