Please WHat is the best book n optical fiber communications

Please i want to know what is the best book in optical fiber communications

it should be easy to understand specially for beginners

and its mathematics hould be simple to understand

thanks

optical communication
by John M senior

PLZ

provide link for optical communications by john senior

thank

Agrawal, G.P. Fiber-Optic Communications Systems (3 ed. Wiley, 2002)