A system for determining wavelengths of a sequence of optical pulses backscattered from sensors distributed along a loop of optical fiber, the system comprising: a loop of optical fiber and sensors distributed along said loop of optical fiber; an optical filter having complementary transmission and reflection coefficients within a predetermined band of wavelengths inclusive of the wavelengths of a sequence of optical pulses backscattered from the sensors distributed along the loop of optical fiber, each of the transmission and reflection coefficients monotonically varying throughout the predetermined band of wavelengths; a first photodetector configured to detect amplitudes of first portions of the sequence of optical pulses backscattered from the sensors distributed along the loop of optical fiber and transmitted through the optical filter, and to generate first output signals indicative of the detected amplitudes of the first portions of the sequence of optical pulses backscattered from the sensors distributed along the loop of optical fiber and transmitted through the optical filter; a second photodetector configured to detect amplitudes of second portions of the sequence of optical pulses backscattered from the sensors distributed along the loop of optical fiber and reflected by the optical filter, and to generate second output signals indicative of the detected amplitudes of the sequence of optical pulses backscattered from the sensors distributed along the loop of optical fiber and reflected by the optical filter; and a calculation engine configured to determine, based on ratios of amplitudes of corresponding first and second output signals, wavelengths of the sequence of optical pulses backscattered from the sensors distributed along the loop of optical fiber, and to determine physical parameters indicated by the wavelengths determined; wherein the system further comprises: a controller configured to generate, at a transmission time, a pulse of optical energy transmitted to the loop of the optical fiber and to associate, based on a time delay between the transmission time and a reception time, each of sequence of optical pulses with a corresponding one of the sensors distributed along the loop of an optical fiber. a loop of optical fiber and sensors distributed along said loop of optical fiber; an optical filter having complementary transmission and reflection coefficients within a predetermined band of wavelengths inclusive of the wavelengths of a sequence of optical pulses backscattered from the sensors distributed along the loop of optical fiber, each of the transmission and reflection coefficients monotonically varying throughout the predetermined band of wavelengths; a first photodetector configured to detect amplitudes of first portions of the sequence of optical pulses backscattered from the sensors distributed along the loop of optical fiber and transmitted through the optical filter, and to generate first output signals indicative of the detected amplitudes of the first portions of the sequence of optical pulses backscattered from the sensors distributed along the loop of optical fiber and transmitted through the optical filter; a second photodetector configured to detect amplitudes of second portions of the sequence of optical pulses backscattered from the sensors distributed along the loop of optical fiber and reflected by the optical filter, and to generate second output signals indicative of the detected amplitudes of the sequence of optical pulses backscattered from the sensors distributed along the loop of optical fiber and reflected by the optical filter; and a calculation engine configured to determine, based on ratios of amplitudes of corresponding first and second output signals, wavelengths of the sequence of optical pulses backscattered from the sensors distributed along the loop of optical fiber, and to determine physical parameters indicated by the wavelengths determined; wherein the system further comprises: a controller configured to generate, at a transmission time, a pulse of optical energy transmitted to the loop of the optical fiber and to associate, based on a time delay between the transmission time and a reception time, each of sequence of optical pulses with a corresponding one of the sensors distributed along the loop of an optical fiber.