SOA-MZI device fault isolation

1. A photonic integrated circuit having a plurality of circuit components, comprising:

an MMI for splitting signal power passing therethrough among first and second optical pathways coupled to first and second outputs, respectively, of the MMI , thereby directing first and second percentages of the signal power along the first and the second optical pathways, respectively; and

a photodetector integrated into the photonic integrated circuit and coupled to said first optical pathway for measuring a signal power level on said first optical pathway,

wherein the photodetector is operable to compare the measured signal power level to a detection threshold, and to signal a fault if the measured signal power is less than the detection threshold.

2. The photonic integrated circuit of claim 1 wherein the second optical pathway is coupled to at least one signal path of the photonic integrated circuit.

3. The photonic integrated circuit of claim 1 wherein the first percentage is between 10% and 50%.

4. A photonic integrated circuit comprising:

a plurality of MMIs (Multi-Mode Interferometers) in the photonic circuit, wherein each said MMI is operable to divide optical energy input thereto between a signal output and a monitoring output, with all of the outputs receiving a non-zero allocation of the input optical energy;

at least two photodetectors operable to receive monitoring output energy from respective monitoring outputs of at least two respective MMIs along respective optical waveguides;

wherein each said photodetector, having a given one of the waveguides leading thereto, is operable to indicate a presence of a fault in the circuit if the monitoring signal energy received along the given waveguide leading thereto is less than a detection threshold, the circuit thereby providing a plurality of photodetector indications; and

wherein the integrated circuit enables isolating a location of the fault within the circuit based on a presence or absence of fault indications at plurality of photodetectors.

5. The photonic circuit of claim 4 wherein the detection threshold of at least one said photodetector is user adjustable.

6. The photonic circuit of claim 4 wherein the photonic circuit enables isolating a location of the fault in the circuit according to a monitoring algorithm.