Measurement of attenuation of an optical fiber using bidirectional transmission of information via the fiber

Apparatus for measuring attenuation of an optical fiber comprising two transceiver units for connection one at each end of the optical fiber, each transceiver unit comprising:

• a port to receive, exteriorly, a connector of the optical fiber to be measured, an optical source, a first detector, a second detector, storage means, coupling means for coupling the optical source and the first detector, alternatively and interiorly, to the port, interiorly, for selectively transmitting optical signals to, and receiving optical signals from, the optical fiber via the port, and data storage means for storing power levels of signals received by the detectors;
• first jumper means having connectors for connecting it between the port and the second detector and second jumper means having connectors for connecting it, alternatively, between the port and the second detector and between the port and the optical fiber, the first jumper means having significantly lower toss characteristics than the second jumper means;
• means for controlling the optical source and the coupling means to supply to the port, alternatively and successively, first, second and third optical signals having the same wavelength and initial power level and storing in the storage means first and second reference power levels of the first and second optical signals measured at the second detector with the first jumper and the second jumper, respectively;
• connected between the port and the second detector;
• means for modulating the third optical signal, prior to transmission via the port, with information representing said second reference power level;
• means for demodulating a detected optical signal received by the first detector via the optical fiber having been transmitted as a said third optical signal by another said transceiver unit connected to a distal end of the optical fiber, to recover information as to the transmitted second reference power level of the detected optical signal as modulated thereupon prior to transmission by said another transceiver unit;
• means for determining attenuation of the optical fiber at the predetermined wavelength using the second reference power level demodulated from the detected optical signal, the first reference power level from the storage means and a measured power lever of the detected optical signal.

A method of measuring attenuation of an optical fiber using a transmitter unit having an optical source, a port, an optical detector and storage means, the port being connected interiorly of the unit to receive light signals from the optical source, and a jumper connected at one end to the port and having at its other end means for connection exteriorly of the unit, alternatively, to an end of optical fiber to be measured and to the optical detector, the method comprising the steps of, at the transmitter:

• connecting said other end of the jumper to the optical detector, transmitting from the source an optical signal having a predetermined wavelength, measuring at the detector a reference power level of the transmitted signal, and storing the measured reference power level in the storage means;
• connecting said other end of the jumper to an adjacent end of the optical fiber;
• transmitting an optical signal having the predetermined wavelength via the jumper to the fiber;
• and
• modulating the optical signal with information identifying the previously measured reference power level;
• and, at a receiver:
• detecting the optical signal received from the fiber;
• demodulating the detected optical signal to recover the transmitted reference power level information;
• monitoring a received power level of the optical signal;
• and
• determining attenuation of the optical fiber at said predetermined wavelength from the recovered transmitted power information and the monitored received power level.

Apparatus for use in measuring attenuation of an optical fiber, comprising:

• an optical source and an optical detector, a port, coupling means coupling the optical source to the port interiorly of the unit, jumper means for connecting at its one end to the port, and at its other end, alternatively to the optical detector and an adjacent end of the optical fiber;
• means for controlling the optical source to supply first and second optical signals both having a predetermined wavelength and the same power level to the port;
• means for storing a first reference power level of the first optical signal measured at said optical detector with the jumper means connected to the detector;
• means for modulating the second optical signal with information identifying the stored first reference power level;
• means for demodulating a detected optical signal received from the detector with the jumper connected to the optical fiber to recover information identifying the transmitted power level modulated thereupon;
• means for determining a power level of the detected optical signal, and means for determining attenuation of the optical fiber from the recovered transmitted power information and the power level of the detected optical signal.