METHOD AND APPARATUS FOR EXTRACTING LIGHT FROM AN OPTICAL WAVEGUIDE

摘要

Apparatus for extracting light from an optical waveguide (12) by bending the
waveguide to such an extent that a portion of any light propagating in the
waveguide leaks therefrom comprises a bending unit (10) for bending a portion
of the waveguide in dependence upon a control signal (S) and providing a
detection signal (Pa) proportional to light leaked from the waveguide. A
control unit (14) varies the control signal (S) in response to the detection
signal (Pa) to cause the bending unit (10) to progressively decrease the
bending angle and has a processor unit (46) which computes a rate of change
(dPa /dR) of the detection signal (Pa) with respect to bending radius (R) and
causes the bending unit to maintain that bending radius at which the aforesaid
rate of change is substantially equal to a predetermined value.