| 摘要 |
<p>Apparatus (Fig. 2) of the type comprising an optical assembly (9), e.g. a lens (11) and reflection grating (13), for collimating light emitted by a laser (L1'), and for refocussing the same onto an output waveguide (7). The waveguide (7) is modified to enhance reflection of the refocussed light, which in turn dominates the resonant response of the laser (L1'). Laser resonance thus depends on geometrical factors, the relative positions of laser (L1') and waveguide (7) and the dispersion properties of the assembly (9). Wavelength selectivity is improved by confining reflection to the core of the waveguide (7) e.g. by using an embedded reflector (17), or further still by using an etalon pair (17, 17'). The laser (L1') may be used in conjunction with other lasers (Ln') and/or detectors, or with retroreflectors (27). A multi-laser input multiplexer (Fig. 2) and single channel drop-and-add devices (Fig. 7; Fig. 10) are described.</p> |
