A monitoring apparatus, capable of being integrated into or coupled to an optical device and adapted to monitor the optical device, the monitoring apparatus comprising: a light source configured to emit light in a first wavelength band, the light coupled onto an optical path in the optical device; a first reflector located at a predetermined location on the optical path, the first reflector configured to reflect light in the first wavelength band and pass light having wavelengths outside of the first wavelength band; a light detector placed and configured to receive and detect light from the optical path that is reflected by the first reflector; and a controller configured to operate the light source, receive signals from the light detector, process the signals received from the light detector repeatedly to perform successive measurements of the optical path, and provide an indication of quality of the optical path based on the successive measurements, wherein the optical device comprises a first component and a second component connected by an optical interconnect, the optical interconnect comprising a portion of the optical path, and wherein the light source is co-located with the first component and the first reflector is co-located with the second component, wherein the optical device is a reconfigurable optical add-drop multiplexer, ROADM, the first component is a wavelength selective switch, WSS, and the second component is an optical cross-connect, OXC,, wherein the monitoring apparatus further comprises a second reflector located at a predetermined location on a second optical path in the optical device, the second optical path having an endpoint separate from an endpoint of the optical path, the second reflector configured to reflect light in a second wavelength band equal to or different from the first wavelength band, and to pass light having wavelengths out of the second wavelength band and wherein: the light source is coupled onto the optical path via the endpoint of the optical path and onto the second optical path via the endpoint of the second optical path concurrently or at a different time; the light source is further configured to emit light in the second wavelength band, the light in the second wavelength band coupled onto the second optical path; and the light detector is further placed and configured to receive and detect light from the second optical path that is reflected by the second reflector. a light source configured to emit light in a first wavelength band, the light coupled onto an optical path in the optical device; a first reflector located at a predetermined location on the optical path, the first reflector configured to reflect light in the first wavelength band and pass light having wavelengths outside of the first wavelength band; a light detector placed and configured to receive and detect light from the optical path that is reflected by the first reflector; and a controller configured to operate the light source, receive signals from the light detector, process the signals received from the light detector repeatedly to perform successive measurements of the optical path, and provide an indication of quality of the optical path based on the successive measurements, wherein the optical device comprises a first component and a second component connected by an optical interconnect, the optical interconnect comprising a portion of the optical path, and wherein the light source is co-located with the first component and the first reflector is co-located with the second component, wherein the optical device is a reconfigurable optical add-drop multiplexer, ROADM, the first component is a wavelength selective switch, WSS, and the second component is an optical cross-connect, OXC,, wherein the monitoring apparatus further comprises a second reflector located at a predetermined location on a second optical path in the optical device, the second optical path having an endpoint separate from an endpoint of the optical path, the second reflector configured to reflect light in a second wavelength band equal to or different from the first wavelength band, and to pass light having wavelengths out of the second wavelength band and wherein: the light source is coupled onto the optical path via the endpoint of the optical path and onto the second optical path via the endpoint of the second optical path concurrently or at a different time; the light source is further configured to emit light in the second wavelength band, the light in the second wavelength band coupled onto the second optical path; and the light detector is further placed and configured to receive and detect light from the second optical path that is reflected by the second reflector. the light source is coupled onto the optical path via the endpoint of the optical path and onto the second optical path via the endpoint of the second optical path concurrently or at a different time; the light source is further configured to emit light in the second wavelength band, the light in the second wavelength band coupled onto the second optical path; and the light detector is further placed and configured to receive and detect light from the second optical path that is reflected by the second reflector.