EoW March 2011

technical article

methods, when applying the RUS limit of 0.1 dB maximum and 0.05 dB average, the cable types generally result in either passing or failing results regardless of the method. 5 The effect of the number of cycles 5.1 Cycles and maximum attenuation peaks The PE-90 test requires that the last of at least five cycles be measured and evaluated. As can be seen in the multiple cycle PE-90 test data in Figures 1 and 2 , the greatest attenuation increases may

not necessarily occur during the fifth cycle and may occur anywhere from cycle two to cycle five. In Figures 1 and 2 , three out of the six cables tested show the greatest attenuation increases between the second and fourth cycles, not the fifth cycle. By only measuring the last cycle, attenuation increases that may occur in the field during the first one or two seasonal temperature extremes may be missed during testing. 5.2 The effect of increasing the number of cycles In order to better understand the effect of mid-span test temperature cycles on attenuation losses, three cables were

The GR-20 specification is as follows: a) Loose tubes stored in a pedestal or closure shall be capable of having a minimum of 14ft of expressed buffer tube stored in a pedestal or closure. b) No greater than 0.15 dB average attenuation increase at 1,550nm on all fibres, during and after the last cycle. 4 PE-90 as compared to GR-20 and FOTP-244 test results 4.1 20-ft PE-90 compared to 14-ft FOTP-244 tube exposure The current specifications outlined in sections 2 and 3 have multiple differences between them, as noted. This section compares methods defined in the PE-90 and GR-20 (referencing FOTP-244) documents by comparing the resulting attenuation loss using identical seg- ments of cables from multiple cable manufacturers. Table 3 is a comparison of results generated from testing identical cable samples to the 20-ft PE-90 method to the 14-ft FOTP-244 method. Four cable samples from two different cable manufactures were tested to both the five cycle PE 90 test method and the two cycle FOTP-244 test method. As can be seen in Table 3 , the 20-ft PE-90 test consistently has higher maximum attenuation changes at –40˚C than the Telcordia GR-20/FOTP-244 14-ft test. The magnitude of this attenuation increase is seen to be in the range of two times higher for the PE-90 method and specification. As will be shown in the next section, the main contributor to this attenuation loss difference is the expressed tube length. 4.2 PE-90 as compared to FOTP-244 method In order to better understand the difference between the test methods of PE-90 and FOTP-244, a 20-ft mid-span test was completed on six different cables, to each test method. The six cables that were tested came from three different cable manufacturers. The 20-ft PE-90 test method and 20-ft FOTP-244 method generally result in similar fibre attenuation changes, as can be seen in Figures 1 and 2 . Figure 1 shows the average attenuation increases and Figure 2 shows the maximum attenuation increases. Out of the six cables tested, four resulted in greater attenuation loss with the FOTP test method over the fifth cycle PE-90 method. While there is variation in the results using the two Table 2 is an outline of these tests.

Figure 2 ▼ ▼ : 20-ft PE-90 and 20-ft draft FOTP-244 midspan test comparison – maximum attenuation increase

Maximum attenuation increase (dB)

Cable 1 Cable 2 Cable 3 Cable 4 Cable 5 Cable 6

Cycle 1 Cycle 4

Cycle 2 Cycle 5

Cycle 3 20ft draft FOTP-244

Figure 3 ▼ ▼ : 20-ft PE-90 mid-span test with five additional cycles – average attenuation increase

Average attenuation increase (dB)

Cycle Cycle Cycle Cycle Cycle Cycle Cycle Cycle Cycle Cycle 1 2 3 4 5 6 7 8 9 10

Cable Type 1

Cable Type 2

Cycle Type 3 abl T 3

120

EuroWire – March 2011