All-in one OTDR Measure OTDR, return, and insertion loss on a single port to characterize optical links(一)

The ever increasing number of subscribers together with increasing demand for more and more bandwidth means providers must install fiber optic cables more quickly. Verifying compliance with system manufacturer specifications is required during the installation and acceptance testing phase [1]. These tests should be easy to perform so that the field operators can run them in less time. The new JDSU tool set offers an integrated test function that reduces testing time and deployment costs. To the best of our knowledge, no other commercially available product combines an OTDR and a loss test set that automatically performs these tests through a single optical connection. In this paper, we present a tool set enabling fast insertion loss (IL) and optical return loss (ORL) measurements using optical continuous wave techniques and characterizing its performance using theoretical analysis and experimental validation. Currently, users can choose among these tested wavelengths 1310, 1550, and 1625 nm.

The tool set comprises a set of two measurement units referred to as Units A and B, each plugged into a base platform. Each unit includes multiple lasers and an optical power meter combined in a single fiber output using a 3-dB coupler as in any OTDR. These devices may operate with continuous wave (CW) light in addition to pulsed light used for OTDR operation. Each base platform may also integrate an additional optical power meter that is required for ORL measurements. For correct operation, users should perform a reference procedure before the link measurement, as Figure 1 shows, which may be completed using either the side-by-side (SbyS) or loopback (LB) method. Additionally, a zero-offset ORL reference is needed for ORL measurements.

The SbyS reference mode can be used to perform IL measurements. The two units are connected to each other, as shown in Figure 1a, using two patch cords, J1 and J2. The reference step enables the power meters for both units to measure the optical power PTx emitted by the laser of the other unit minored by the IL of the two patch cords.

However, it may not always be possible to perform this procedure because of the distance between each end of the link being tested; therefore, technicians can use the LB reference mode, as described in Figure 1b, where each of the units is connected to the power meter of its base platform. During the LB reference, the insertion loss of the patch cord, ILpatch cord, is first estimated as the difference between the measured power and the factory calibrated power.