Patent ID: 6501872
Filing Date: 2002-12-31
Classification: H04J

Abstract:
An apparatus for optical add/drop multiplexing of a wavelength channel multiplex, said apparatus comprising an MMI coupler (1) at least of size 4Ã—4 and an MI arm section (3);said MMI coupler including a multiplex input terminal (5) for input of said wavelength channel multiplex into said MMI coupler, an add channel input terminal (9) for input of a wavelength channel to be added to said multiplex into said MMI coupler, a drop channel output terminal (13) for output of a wavelength channel to be dropped from said multiplex from said MMI coupler, a multiplex output terminal (17) for output of said wavelength channel multiplex from said MMI coupler, and at least four input/output terminals (21, 23, 25, 27); and said MMI coupler being effective to split light incoming on one of its input terminals into light shares delivered onto its input/output terminals, and to combine light shares incoming on its input/output terminals into combined light delivered onto one of its output terminals in dependence on the mutual phase relation of the incoming light shares; and said MI arm section including at least four waveguides (29, 31, 33, 35), of which each is optically connected to a respective one of said input/output terminals of the MMI coupler, and of which each of all, or of all but one, of the waveguides is at least provided with, as seen from the MMI coupler, a first phase control element (37), a narrow band reflection grating (39), a second phase control element (47), and a wide frequency range reflection means (51); each of said narrow band reflection gratings being provided with a heater means for tuning the respective narrow band reflection grating to the wavelength channel to be added and/or to the wavelength channel to be dropped; said first phase control elements being effective to direct the channel to be added to the multiplex output terminal of the MMI coupler and/or to direct the channel to be dropped to the drop channel output terminal of the MMI coupler; said wide frequency range reflection means being effective to reflect all wavelength channels comprised in the input wavelength channel multiplex except the wavelength channel to be dropped; and said second phase control elements being effective to direct all wavelength channels comprised in the input wavelength channel multiplex except the wavelength channel to be dropped to the multiplex output terminal of the MMI coupler.