2.2 Intermodal Dispersion 51 (ZiFr 4 ) in order to realize the low loss that is potentially possible by operating at these wavelengths [KK97, p. 69]. 2.1.1 Bending Loss Optical fibers need to be bent for various reasons both when deployed in the field and particularly within equipment. Bending leads to "leakage" of power out of the fiber core into the cladding, resulting in additional loss. A bend is characterized by the bend radius--the radius of curvature of the bend (radius of the circle whose arc approximates the bend). The "tighter" the bend, the smaller the bend radius and the larger the loss. The bend radius must be of the order of a few centimeters in order to keep the bending loss low. Also, the bending loss at 1550 nm is higher than at 1310 nm. The ITU-T standards specify that the additional loss at 1550 nm due to bending must be in the range 0.5­1 dB, depending on the fiber type, for 100 turns of fiber wound with a radius of 37.5 mm. Thus a bend with a radius of 4 cm results in a bending loss of < 0.01 dB. However, the loss increases rapidly as the bend radius is reduced, so that care must be taken to avoid sharp bends, especially within equipment.