In a modular data acquisition system, a module comprises at least one analog-to-digital converter for converting an analog input signal into a digital signal, and a clock generating circuit for supplying an internal clock signal. The positioning structure includes a first plate, a second plate and a connecting plate connected between the first plate and the second plate. An insulating material can be formed in the groove on the conductive material that has an etch selectivity with respect to the insulating layer. 2, and z is a number from 0 to 0. A non-linear optical medium section is formed in one of the waveguides and is capable of self-phase modulating each channel of an N-channel multiplexed lightwave to produce an output lightwave having improved channel power uniformity. The positive and negative electrode plates are wound with the separator interposed therebetween, thereby to form an electrode plate assembly.