Apparatus and method for amplifying laser signals using segments of fibers of differing core diameters andor differing cladding diameters to suppress amplified spontaneous emission and non-linear effects such as four-wave mixing, self-phase modulation, and stimulated Brillouin andor Raman scattering. At least one LED is mounted to the front side of the MCPCB. The valve also includes one or more seal portions positioned on the valve so as to block both a vent passage, the chemical or the carrier fluid passages when said valve is in the closed position.