An optical branching component particularly suitable for use as a tap
device is described. The component has two optical waveguides coupled
between two optical couplers which each include at least one MMI
supporting at least two guided modes. There is an effective optical path
length difference between the two waveguides and the coupling strength of
at least one of the couplers monotonically decreases with increasing
wavelength in the operational wavelength region of the component. This
means a coupler with relatively large coupling strength and relatively
low polarization dependency can be used in the component, giving low
polarization dependent variation in the tap ratio, particularly for small
tap ratios. Moreover, the use of MMIs in the couplers avoids the need to
fabricate to a high process tolerance very small gaps between two
waveguides, as can be the case with directional couplers used in prior
art branching component designs.