An optical link consists of three segments: the first segment is $50$ long with a dispersion of $16$ ps$/($nm$-$km$),$ the second segment is $30$ km long with a dispersion of$-10$ ps$/($nm$-$km$),$ and the third segment is $40$ km long with a dispersion of $18$ ps$/($nm$-$km$).$ Calculate the net dispersion of the entire optical link. Provide detailed calculations anda discuss how dispersion management techniques can improve the performance of the optical communication system.