## Abstract

We have theoretically and experimentally investigated an optical fiber with circular polarization modes on one end and linear polarization modes on the other end. We call this fiber a polarization-transforming fiber because the local modes, or polarization states they represent, are converted from linear to circular, and visa versa, in the fiber. We have developed and implemented a postdraw process for making polarization-transforming fiber samples 30 mm long with losses less than 1 dB and a polarization-mode conversion from circular to linear greater than 20 dB. Also, we have modeled and measured the dependence on wavelength and temperature of polarization-transforming fiber samples. The measured normalized wavelength dependence of a sample fiber 30 mm long was approximately 1.4 × 10^{-4} nm^{-1}, and the measured normalized temperature dependence was approximately 6 × 10^{-4} °C^{-1}. These values are better in some cases than values for conventional high-birefringent fiber quarter-wave plates.

© 2003 Optical Society of America

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### Equations (13)

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(1)
$$\frac{\mathrm{d}A\left(z\right)}{\mathrm{d}z}=K\left(z\right)A\left(z\right),K\left(z\right)=\left[\begin{array}{cc}j\frac{\mathrm{\Delta}\mathrm{\beta}}{2}& \mathrm{\tau}\left(z\right)\\ -\mathrm{\tau}\left(z\right)& -j\frac{\mathrm{\Delta}\mathrm{\beta}}{2}\end{array}\right],$$
(2)
$$O\left(z\right)=\left[\begin{array}{cc}cos\mathrm{\varphi}\left(z\right)& isin\mathrm{\varphi}\left(z\right)\\ isin\mathrm{\varphi}\left(z\right)& cos\mathrm{\varphi}\left(z\right)\end{array}\right],$$
(3)
$${E}_{R}\left(z\right)=-10{log}_{10}\left[\frac{|{A}_{x}\left(z\right){|}^{2}}{|{A}_{y}\left(z\right){|}^{2}}\right],$$
(4)
$${\mathrm{\tau}}_{\mathit{Li}}\left(z\right)=\frac{2\mathrm{\pi}\mathrm{\tau}\left(0\right)}{{L}_{R}}\left({L}_{R}-z\right),$$
(5)
$${\mathrm{\tau}}_{exp}\left(z\right)=2\mathrm{\pi}\mathrm{\tau}\left(0\right)exp\left(\frac{-\mathit{az}}{{L}_{R}}\right),$$
(6)
$${\mathrm{\tau}}_{cos}\left(z\right)=\mathrm{\pi}\mathrm{\tau}\left(0\right)\left[1+cos\left(\frac{\mathrm{\pi}z}{{L}_{R}}\right)\right].$$
(7)
$${L}_{b}\left(\mathrm{\lambda},T\right)=\frac{\mathrm{\lambda}}{\mathrm{\Delta}n\left(\mathrm{\lambda},T\right)},$$
(8)
$$\frac{1}{{L}_{b}}\frac{\mathrm{d}{L}_{b}}{\mathrm{d}\mathrm{\lambda}}=\frac{1}{\mathrm{\lambda}}-\frac{1}{\mathrm{\Delta}n}\frac{\mathrm{d}\mathrm{\Delta}n}{\mathrm{d}\mathrm{\lambda}},$$
(9)
$$\frac{1}{{L}_{b}}\frac{\mathrm{d}{L}_{b}}{\mathrm{d}T}=-\frac{1}{\mathrm{\Delta}n}\frac{\mathrm{d}\mathrm{\Delta}n}{\mathrm{d}T}.$$
(10)
$$\left[\begin{array}{c}{A}_{x}\\ {A}_{y}\end{array}\right]\cong \frac{1}{2}\left[\begin{array}{cc}1& \pm 1\\ \pm 1& 1\end{array}\right]\times \left[\begin{array}{cc}exp\left(i\mathrm{\delta}/2\right)& 0\\ 0& exp\left(-i\mathrm{\delta}/2\right)\end{array}\right]\frac{\sqrt{2}}{2}\left[\begin{array}{c}-i\\ 1-{\mathrm{\epsilon}}_{C}\end{array}\right],$$
(11)
$${I}_{\pm}\cong \frac{1}{4}\left[1+{\left(1-{\mathrm{\epsilon}}_{C}\right)}^{2}\pm 2\left(1-{\mathrm{\epsilon}}_{C}\right)cos\mathrm{\epsilon}\prime \right].$$
(12)
$${E}_{R}=\frac{{I}_{-}}{{I}_{+}}\cong \left(1-{\mathrm{\epsilon}}_{C}\right)\frac{\mathrm{\epsilon}{\prime}^{2}}{2},$$
(13)
$$\mathrm{\epsilon}\prime \cong {\left[\frac{2{E}_{R}}{\left(1-{\mathrm{\epsilon}}_{C}\right)}\right]}^{1/2}.$$