MEMS wavelength selectable switch for adaptive wavelength filtering
A MEMS-based Wavelength Selectable Switch (WSS), used classically for demultiplexing fiber optic communications, is re-purposed to act as a filter. A light emitter provides a light beam with its wavelength detected by a wavelength detector. A light condenser directs reflected light from the light emitter to an input of the WSS. The WSS is controllable to provide a selected wavelength band to a selected output of the WSS, where it is detected by a photodetector. Other wavelengths are discarded by the WSS at other outputs. A controller is configured to control the WSS to select the selected wavelength band based on a detected wavelength from the wavelength detector.
1. A micro-electromechanical system (MEMS) apparatus for beam steering in a Light Detection and Ranging (LiDAR) system of an autonomous vehicle, the apparatus comprising:
a laser diode emitting a laser beam;
a laser beam wavelength detector;
a MEMS-based Wavelength Selectable Switch (WSS), controllable to provide a selected wavelength band to an output of the WSS;
a light condenser for directing reflected light from the laser diode to an input of the MEMS-based Wavelength Selectable Switch;
at least one detector for detecting the selected wavelength band from the output of the WSS; and
a controller configured to control the WSS to select the selected wavelength band based on a detected wavelength from the laser beam wavelength detector,
wherein the selected wavelength band of the WSS is 25 nanometers or less,
wherein the WSS includes a reflective MEMS mirror array, an optical circulator, a grating, a single input and a plurality of outputs, the optical circulator is connected to a fiber cable which receives reflected light from the light condenser and the optical circulator provides the reflected light to the WSS and receives back the selected wavelength band from the WSS and provides the selected wavelength band to the detector.
2. The apparatus of claim 1 wherein the WSS is a transmissive WSS.
3. The apparatus of claim 1 wherein the laser beam wavelength detector comprises a thermistor.
4. The apparatus of claim 1 further comprising:
a heater mounted proximate to the laser diode;
a thermistor mounted proximate to the laser diode;
the controller being coupled to the heater to cause the heater to maintain a temperature output of the thermistor to above a designated temperature level that will maintain the wavelength of the laser beam within the selected wavelength band;
wherein the controller provides a varying voltage level to the heater to maintain the temperature output of the thermistor to above the designated temperature level; and
wherein the heater comprises at least one resistor.
5. The apparatus of claim 4 wherein the heater comprises at least one resistor.
6. The apparatus of claim 1 further comprising:
additional outputs of the WSS connected to a black light dump; and
the controller being configured to control the WSS to select wavelengths other than the selected wavelength band to be directed to the additional outputs.