Switching is achieved by simply sliding one half of the circuit past the other. This is readily done by activating a DC motor which is incorporated in the stage to move the sliding platform. Logic circuitry determines the distance moved. Any one of the 12 fibres can be used as the input to switch to the 12 output fibres. The 1 x 24 version of the switch is similar, except for the waveguide configuration and the use of a faster stepping motor to drive the sliding platform. The waveguide circuit is shown in Fig. 3; it consists of a single input guide and 24 output waveguides which are tapered towards the coupling region to a spacing of 5 0 p. At the output end, the waveguides are spaced by 2 5 0 p and are grouped in units of 12 to allow the fibre connector arrays to be attached. Switch performance: The switches were evaluated with regards to loss, back reflection, cross-talk, switching time and repeatability. The insertion loss for both switches was 0.2dB, not including the fibre-to-waveguide interconnection loss, the sum of which for both sides amounts to-1dB. The back reflection and cross-talk were also the same for both switches, being 4 5 and-55dB, respectively.The back reflection value can be lowered by the use of angled ends which could be added dwing polishing. The cross-talk value was at the limit of measurement and may be lower. It also indicates the possibility of spacing the fibres closer than 50pm. The switching speed for the 1 x 12 switch was 300mm/s, limited by the DC motor driving the sliding platform. The 1 x 24 switch with its faster stepping motor had a switching speed of 3 d s. Thus, the 24 waveguides could be scanned in just 0.4s. The maximum switching time of the 1 x 12 switch can, of course, be reduced from 10 to 0.2s with a similarly fast motor and tapered, closely spaced, waveguides. The repeatability of both models was also the same, being 0.05dB. It should be noted that, like the waveguides themselves, the switches are wavelength-and polarisation-insensitive. Conclusion: We have presented a mechanical silica optical circuit switch using planar waveguide technology having some unique properties. The switch has low loss and low cross-talk, in addition to being polarisation-and wavelength-independent. It has a small size and a low assembly cost. The switch is latchable, drawing no power to remain in the selected configuration. While we have presented 1 x 12 and 1 x 24 versions, the switch is readily expandable to a much larger number of ports. The
Experimental results of time delay ripples in dispersion compensating fiber Bragg gratings fabricated with either holographic or electron-beam written 10-cm-long phase masks are presented. Deviations from linear phase delay are dependent upon UV exposure uniformity and phase mask errors.
The emission of a broad-area laser always contains several lateral modes (along the junction plane) even at low drive levels. To increase the discrimination against high-order lateral modes, we developed simple techniques for depositing a profiled thin layer of SiO on the output facet of a broad-area laser that has a 75-μm-wide injection current stripe. The profiled coating provided a nearly Gaussian reflectivity in the lateral direction (parallel to the junction plane). The resolved near-field spectra of the uncoated and coated lasers have been compared. The maximum output power in the single-lateral-mode regime was pushed to 25 mW with the profiled coating, compared with a corresponding power of less than 1 mW before deposition. Experimental results have confirmed the behavior predicted by our numerical simulations. This method is scalable to higher-power lasers.
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