An access gate (100, 200, 300) for detecting movement through the access gate (100, 200, 300), the access gate (100, 200, 300) comprising: a first optical emitter (210, 310) provided on a first side (101, 201, 301) of the access gate (100, 200, 300), wherein the first optical emitter (210, 310) is configured to transmit a first beam (230, 330) of light in a direction perpendicular to a direction of movement through the access gate (100, 200, 300); a first plurality of optical receivers (220, 320) provided on a second side (102, 202, 302) of the access gate (100, 200, 300), wherein each of the first plurality of optical receivers (220, 320) is configured to detect when the first beam (230, 330) of light is received at each of the first plurality of receivers (220, 320), wherein an angle of the first beam of light (230, 330) emitted from the first optical emitter (210, 310) is sufficiently wide for each of the first plurality of optical receivers (220, 320) to receive the beam of light when a path of the beam of light is uninterrupted; a second optical emitter (211, 311) provided on the second side (102, 202, 302) of the access gate (100, 200), wherein the second optical emitter (211, 311) is configured to transmit a second beam (231, 331) of light in a direction opposite to that of the first beam (230, 330) of light; a second plurality of optical receivers provided on the first side (101, 201, 301) of the access gate (100, 200), wherein each of the second plurality of optical receivers is configured to detect whether or not the second beam of light (231, 331) is received thereat; characterized in that the access gate comprises a module configured to monitor output signals from the optical receivers (220, 320, 221) periodically or on an ongoing basis and if the intensity of the monitored output signals is drifting and the drift is below a threshold, then adjust the transmit intensity of the optical emitters such that the intensity of the monitored output signals remains within one or more thresholds that ensure reliable operation of the access gate, and if the drift exceeds the threshold, generate an alert to replace components including at least one of optical emitters (210, 310, 211, 311) or optical receivers (220, 320, 221) or to manually adjust the threshold. a first optical emitter (210, 310) provided on a first side (101, 201, 301) of the access gate (100, 200, 300), wherein the first optical emitter (210, 310) is configured to transmit a first beam (230, 330) of light in a direction perpendicular to a direction of movement through the access gate (100, 200, 300); a first plurality of optical receivers (220, 320) provided on a second side (102, 202, 302) of the access gate (100, 200, 300), wherein each of the first plurality of optical receivers (220, 320) is configured to detect when the first beam (230, 330) of light is received at each of the first plurality of receivers (220, 320), wherein an angle of the first beam of light (230, 330) emitted from the first optical emitter (210, 310) is sufficiently wide for each of the first plurality of optical receivers (220, 320) to receive the beam of light when a path of the beam of light is uninterrupted; a second optical emitter (211, 311) provided on the second side (102, 202, 302) of the access gate (100, 200), wherein the second optical emitter (211, 311) is configured to transmit a second beam (231, 331) of light in a direction opposite to that of the first beam (230, 330) of light; a second plurality of optical receivers provided on the first side (101, 201, 301) of the access gate (100, 200), wherein each of the second plurality of optical receivers is configured to detect whether or not the second beam of light (231, 331) is received thereat;