In one aspect the invention provides an optical circuit enclosure
enclosing at least one optical circuit or optical circuit component; the
enclosure comprises: a tray type container containing at least one
optical circuit or optical circuit component; a tray type closure member
closing the container; the closure member containing at least one further
optical circuit component on an external side thereof for optically
connecting the enclosed component to an external optical circuit; and
sealing means providing a moisture resistant seal between the container
and the closure member.