n Usage Pattern: Before buying OFC one should look where it is to be deployed—access or longhaul. If it is deployed for access purpose than one has to opt for a lower count fiber. For longhaul purposes like connecting two cities one has to opt for a higher count fiber as the traffic capacity is on a higher side. Even on the access front, depending upon residential and commercial users the fiber count increases or decreases accordingly.

One also has to take into consideration how the cable is to be laid. If it is to be hanged in the ground than one has to opt for a lighter cable.

n Pricing: The key buying parameter in government (BSNL, MTNL, and Indian Railways) tenders is the price as long as the optical fiber cables meet the required specifications. On the other hand, the private operator, which contributes a small portion of the overall OFC sales in the country, pays more stress on the quality of fiber. While buying optical fiber cables, carriers and enterprise customers should focus more on optical parameters, as most of the problems are due to impurity of glass and pricing should not be the only criteria.

n Dispersion Slope: Different fiber manufacturers have different dispersion slopes, which is proprietary. Different OFC manufacturers in the country use different standards, which is just a marketing issue. Lower the dispersion slope, the better it is.

n End-to-End Attenuation: The reduction in signal strength is measured as attenuation and the unit is decibel (dB). The light passing through fiber will not disperse if the fiber cladding is uniform throughout the length of the fiber. So attenuation loss can be minimized if there is uniformity. The permissible limit for 1,310 nm is 0.38 dB/km while for 1,550 nm it is 0.22 dB/km.

If the attenuation level decreases, it is good, but if it increases then one has to increase the number of repeaters, which will result in an increase in transmission cost. In majority of fibers, the attenuation loss varies from 0.19 dB/km to 0.33 dB/km and there is an increase of 0.01 dB/km once the fiber is transformed into OFC.

n Attenuation Under Stressful Condition: Under this condition, OFC is put under stress and the cable is tied on either side, and 2.7 Newton weight is applied on both the sides. The maximum attenuation variation should be 0.4 to 0.5 percent. Once OFC is relaxed, it comes back to the normal position. Under pressure, the cable should not break. This is used mainly for duct and buried type of OFC.

The buyer should also look at other mechanical and optical properties like mode field concentricity (shows how uniform an OFC is), cut-off wavelength, splice loss, and fiber loss per km (dependent on the transmission equipment).

n Polarized Mode Dispersion: This tests the optical characteristics of OFC in polarized mode whereby one can test how much light goes out and how much light remains inside the fiber.

n Chromatic Dispersion: It depicts the number of wavelength that is attenuated and the strength of the signal.