Fiber span characterization utilizing paired optical time domain reflectometers

A system for characterizing an optical fiber span extending between a first optical node at a near-end termination of the optical fiber span and a second optical node at a far-end termination of the optical fiber span, comprising

• a near-end optical time domain reflectometer (OTDR) coupled to the near-end termination of the optical fiber span;
• a far-end OTDR coupled to the far-end termination of the optical fiber span,
• the near-end OTDR and the far-end OTDR each including a light source for injecting an optical probe operating at a same probe wavelength into the optical fiber span, a receive component for measuring back-reflected light from the optical probe, and a processing module for generating an OTDR trace based on the back-reflected light measurements, the near-end and far-end processing modules configured to control an operation of both the near-end and far-end OTDRs such that only one of the near-end and far-end OTDRs are in operation at any point in time, the near-end processing module producing a near-end OTDR trace and the far-end processing module producing a far-end OTDR trace;
• and
• a characterization element in communication with both the near-end OTDR and the far-end OTDR, the characterization element for combining the near-end OTDR trace with the far-end OTDR trace in a trace-stitching procedure to create as an output an end-to-end OTDR trace that characterizes the optical fiber span, wherein the characterization element is configured to estimate an optical signal loss based on measurements performed by the near-end and far-end OTDRs, utilizing the estimated optical signal loss to determine a mid-point of the optical signal as used by the trace-stitching procedure.

A system for characterizing an optical fiber span extending between a first optical node at a near-end termination of the optical fiber span and a second optical node at a far-end termination of the optical fiber span, comprising

• a near-end optical time domain reflectometer (OTDR) coupled to the near-end termination of the optical fiber span;
• a far-end OTDR coupled to the far-end termination of the optical fiber span,
• the near-end OTDR and the far-end OTDR each including a light source for injecting an optical probe operating at a same probe wavelength into the optical fiber span, a receive component for measuring back-reflected light from the optical probe, and a processing module for generating an OTDR trace based on the back-reflected light measurements, the near-end and far-end processing modules configured to control an operation of both the near-end and far-end OTDRs such that only one of the near-end and far-end OTDRs are in operation at any point in time, the near-end processing module producing a near-end OTDR trace and the far-end processing module producing a far-end OTDR trace;
• and
• a characterization element in communication with both the near-end OTDR and the far-end OTDR, the characterization element for combining the near-end OTDR trace with the far-end OTDR trace in a trace-stitching procedure to create as an output an end-to-end OTDR trace that characterizes the optical fiber span, wherein the near-end light source comprises a multi-wavelength optical light source, and the characterization element is further configured to provide a measurement of optical path length as a function of wavelength, based upon the transit time of the optical probe from the near-end multi-wavelength light source to the far-end receive component, the characterization element recording each estimated path length with an associated optical probe wavelength.

A system for characterizing an optical fiber span extending between a first optical node at a near-end termination of the optical fiber span and a second optical node at a far-end termination of the optical fiber span, comprising

• a near-end optical time domain reflectometer (OTDR) coupled to the near-end termination of the optical fiber span;
• a far-end OTDR coupled to the far-end termination of the optical fiber span,
• the near-end OTDR and the far-end OTDR each including a light source for injecting an optical probe operating at a same probe wavelength into the optical fiber span, a receive component for measuring back-reflected light from the optical probe, and a processing module for generating an OTDR trace based on the back-reflected light measurements, the near-end and far-end processing modules configured to control an operation of both the near-end and far-end OTDRs such that only one of the near-end and far-end OTDRs are in operation at any point in time, the near-end processing module producing a near-end OTDR trace and the far-end processing module producing a far-end OTDR trace;
• and
• a characterization element in communication with both the near-end OTDR and the far-end OTDR, the characterization element for combining the near-end OTDR trace with the far-end OTDR trace in a trace-stitching procedure to create as an output an end-to-end OTDR trace that characterizes the optical fiber span, wherein the near-end OTDR is configured to include an adjustable polarization controller positioned at an output of the near-end light source, the adjustable polarization controller responsive to commands from the characterization element to change a state of polarization of the generated optical probe as a function of time, the characterization element using measurements of received optical power over time at the far-end receive component to determine a polarization-dependent loss of the optical fiber span.

A method of forming an end-to-end OTDR trace of an optical fiber span, the method including the steps of:

• performing a first OTDR procedure from a first, near-end termination of the optical fiber span, using a near-end OTDR module to transmit a near-end optical probe operating at a known wavelength and measure back-reflected optical power associated with the near-end optical probe, generating therefrom a near-end OTDR trace;
• performing a second OTDR procedure from a second, far-end termination of the optical fiber span, using a far-end OTDR module to transmit a far-end optical probe operating at the known wavelength and measure back-reflected optical power associated with the far-end optical probe, generating therefrom a far-end OTDR trace;
• estimating a span-based parameter of the optical fiber span;
• defining an OTDR trace stitching point as a mid-point of the estimated span-based parameter;
• starting at the stitching point of the far-end OTDR trace, identify loss values for a set of individual span locations from the stitching point to the far-end termination of the optical fiber span;
• adding an inverse of each identified loss value to the near-end OTDR trace to form a combined OTDR trace of the optical fiber span;
• and
• inserting anomalies present in the far-end OTDR trace at defined locations into the combined OTDR trace, forming as an output the end-to-end OTDR trace of the optical fiber span.