Abstract: A device for adding and/or dropping a signal to a transmission line. First and second optical circulators are connected by at least one switchable grating reflector, whereby a grating reflector can be switched into or out of the connecting path between the two circulators. A plurality of optical signals, each centered about a different wavelength, is coupled to a first port of the first circulator; these signals appear at the second port thereof. If a grating reflector capable of reflecting .lambda..sub.i is switched into the circuit, the signal centered about .lambda..sub.i propagates from the second port of the first circulator and reflects from the grating reflector back into the second port and out of the third port. The remainder of the input signals that are not reflected by grating reflectors propagate into the first port and from the second port of the second circulator as an output thereof. Also, a signal at wavelength .lambda..sub.