Optical Window Assembly for An Optical Sensor of A Downhole Tool and Method of Using Same

An optical window assembly of an optical sensor of a downhole tool positionable in a wellbore penetrating a subterranean formation. The downhole tool has a housing with a flowline therethrough to receive downhole fluid therein. The optical sensor is positionable about the flowline to measure light passing therethrough. The optical window assembly includes a tubular sensor body positionable in the housing (the sensor body having a sensor end and a flanged signal end with a passage therethrough), an optical window positionable in the passage of the sensor body to pass the light from the flowline to the optical sensors, a seal disposable about the sensor body, and a backup ring disposable about the sensor body between the flanged signal end and the seal to support the seal about the sensor body whereby the downhole fluid is prevented from leaking between the seal and the sensor body.