The problem is that u are using Single mode optics with multimode fibers. Damping wise and light wise this will be a problem
Single-mode and multi-mode
Fiber optic cable is available in single-mode and multi-mode types. Multi-mode cable has a larger core diameter (50um o
r
62.5um) than single-mode fiber (9um core diameter). When light travels down multi-mode fiber it is reflected at different angle
s as it
propagates down the transmission path. These multiple reflections cause the light to spread out in time as it propagates down
the fiber,
making it more difficult for the receiver to recover the data. Single-mode fiber being much narrower, confines the optical sign
al to a
straighter path with fewer reflections. As a result, optical signal dispersion is significantly reduced, which translates into
a cleaner
sig-
nal. Longer transmission lengths can therefore be achieved with single mode
cable. It is also a
bonus that
single-mode fiber can
now
be purchased for the same or less than multi-mode fiber.
Single-mode and multi-mode cable should not be mixed in the same system. However, if really necessary, it is possible to use
multi-mode fiber downstream of single-mode fiber, as the larger diameter multi-mode fiber will collect most of the light emitte
d from
the single mode fiber. You can never use single mode fiber, or any single-mode components such as CWDM devices, downstream of
multi-mode fiber.