An optical wavelength division multiplexor module (40) has a housing (44) having a front face (45) and a rear face (46). The wavelength division multiplexor module (40) comprises a short wavelength path terminal (41), a common optical terminal (42), and a long wavelength path terminal (43). The short wavelength path terminal (41) comprises a first fiber optic adapter (48), for engaging a fiber optic connector of a first patch cable (24), while the common optical terminal (42) comprises a second fiber optic adapter (48), for engaging a fiber optic connector of a second patch cable (26). The long wavelength path terminal (43) comprises a fiber optic connector (49) for directly engaging with a fiber optic adapter (48) carried on a modified optical test access switch (50). The short wavelength path terminal (41) and the common optical terminal (42) are both provided on the front face (45) of the housing (44), while the long wavelength path terminal (43) is provided on the rear face (46) of the housing (44).