Particulate matter detector and method for detecting particulate matter

A method for detecting particulate matter, the method comprising:

• during a measurement phase:
• accumulating particulate matter from a gaseous environment directly on a cladding-free surface of a first waveguide within an interrogation region;
• guiding light from a light emitter through the first waveguide to a waveguide splitter at a first intensity;
• splitting by means of the waveguide splitter at least a portion of the light from the first waveguide into a second waveguide that is coupled to a detector;
• detecting an intensity of light within the second waveguide and determining a change in the intensity of the light detected by the detector;
• and
• outputting an indication of an opacity of the surface of the first waveguide with the accumulated particulate matter thereon based on the determined change;
• and
• during a cleaning phase:
• guiding light from the light emitter through the first waveguide to the waveguide splitter at a second intensity that is larger than the first intensity;
• splitting by means of the waveguide splitter at least a portion of the light from the first waveguide into a third waveguide that is free of cladding;
• and
• directing the accumulated particulate matter from the interrogation region to the third waveguide via optical forces.

A particulate matter detector, comprising:

• a light emitter configured to emit light;
• a first, a second and a third waveguide, the third waveguide being free of cladding;
• a waveguide splitter;
• a detector;
• and
• a controller,
• wherein the first waveguide is coupled to the light emitter and is configured to guide the emitted light towards the waveguide splitter, the first waveguide comprising an interrogation region formed by a cladding-free surface of the first waveguide, the surface being exposed to a gaseous environment and configured to accumulate directly thereon particulate matter from the gaseous environment;
• wherein the waveguide splitter couples the interrogation region of the first waveguide to the second waveguide and to the third waveguide;
• wherein the detector is coupled to the second waveguide and configured to detect an intensity of light that is split from the interrogation region into the second waveguide by the waveguide splitter;
• wherein the third waveguide is configured as a dump for particulate matter that has accumulated on the cladding-free surface of the first waveguide;
• and
• wherein the controller is configured to
• during a measurement phase, set a first intensity of the light coupled into the first waveguide, determine a change in the intensity of the light detected by the detector, and output an indication of an opacity of the surface of the first waveguide with the accumulated particulate matter thereon based on the determined change;
• and
• during a cleaning phase, set a second intensity of the light coupled into the first waveguide that is larger than the first intensity for directing the accumulated particulate matter from the interrogation region to the third waveguide via optical forces.