A fiber optic adapter comprising: a housing defining an open-ended first through-channel having a first port at one end and a second port at another end, the first and second ports (160, 164) being configured to receive first and second fiber optic connectors (121, 123), respectively, the housing comprising an aperture opening into the first through-channel laterally; a cover comprising a cylinder with a bore, the cover positioning the cylinder inside the first through-channel; and an alignment sleeve positioned inside the bore, the alignment sleeve comprising an open-ended second through-channel configured to receive a first ferrule of the first fiber optic connector and a second ferrule of the second fiber optic connector, the cover comprising a closure portion that closes the aperture of the housing a shutter door adjacent the first port, the shutter door being movable between an open position and a closed position; and a biasing member configured to bias the shutter door toward the closed position, the shutter door being configured to be automatically transitioned to the open position when the first fiber optic connector is inserted into the first port and to be automatically transitioned to the closed position by the biasing member when the first fiber optic connector is removed from the first port, wherein the shutter door comprises an outward facing surface with at least one engagement projection extending outwardly therefrom, and the at least one engagement projection is configured to engage a front portion of the first fiber optic connector when the first fiber optic connector is inserted into the first port, characterised in that: the at least one engagement projection is configured to avoid contacting an end face of a ferrule of the first fiber optic connector when the first fiber optic connector is inserted into the first port, and the at least one engagement projection prevents the outward facing surface of the shutter door from contacting the end face of the ferrule when the first fiber optic connector is inserted into the first port. a housing defining an open-ended first through-channel having a first port at one end and a second port at another end, the first and second ports (160, 164) being configured to receive first and second fiber optic connectors (121, 123), respectively, the housing comprising an aperture opening into the first through-channel laterally; a cover comprising a cylinder with a bore, the cover positioning the cylinder inside the first through-channel; and an alignment sleeve positioned inside the bore, the alignment sleeve comprising an open-ended second through-channel configured to receive a first ferrule of the first fiber optic connector and a second ferrule of the second fiber optic connector, the cover comprising a closure portion that closes the aperture of the housing a shutter door adjacent the first port, the shutter door being movable between an open position and a closed position; and a biasing member configured to bias the shutter door toward the closed position, the shutter door being configured to be automatically transitioned to the open position when the first fiber optic connector is inserted into the first port and to be automatically transitioned to the closed position by the biasing member when the first fiber optic connector is removed from the first port, wherein the shutter door comprises an outward facing surface with at least one engagement projection extending outwardly therefrom, and the at least one engagement projection is configured to engage a front portion of the first fiber optic connector when the first fiber optic connector is inserted into the first port, characterised in that: the at least one engagement projection is configured to avoid contacting an end face of a ferrule of the first fiber optic connector when the first fiber optic connector is inserted into the first port, and the at least one engagement projection prevents the outward facing surface of the shutter door from contacting the end face of the ferrule when the first fiber optic connector is inserted into the first port. the at least one engagement projection is configured to avoid contacting an end face of a ferrule of the first fiber optic connector when the first fiber optic connector is inserted into the first port, and the at least one engagement projection prevents the outward facing surface of the shutter door from contacting the end face of the ferrule when the first fiber optic connector is inserted into the first port.