Source Coupling
    The Source Coupling section is fairly accurate, presenting ideas to the reader, and even better it uses different scenarios and situations to make the user identify with what is going on, but its suggestions and answers are too general, vague and imprecise.
For example when mentioning the light source should be selected carefully because it might not be symmetrical and spread light in part 3, it would be better to hit the nail on the head and suggest that a monochromatic, symmetrical light source such as a laser would be more efficient than an ordinary incandescent light bulb. (efficient source coupling address)
    Also, in losses from source coupling part 1 and 2, it plants the seed of which diameter is better for a light source and if a gap is desirable, but it does not follow it up. It should tell you that a light source whose diameter is bigger than the fibre and is butted directly at the end of the fibre is desired because it had a steady-state distribution which launches equal amounts of power into every mode of the fibre, rather than a source whose area is smaller than the fibre core cross sectional area, and/or which leaves a gap, because it excites different mode groups to a different degree.
     It also doesn’t mention when steady-state power distribution is asserted, the total power decays with an exponential loss.
 Losses from source coupling goes on to indicate that the rays greater than the critical angle will be lost, but they don’t provide a more detailed theory or solutions such as: