Wavelength References offers its HCN-Mini fiber-coupled miniaturized hydrogen cyanide gas absorption cell. Designed for embedded OEM applications in harsh environments, the cells feature hard, sealed, glass gas tubes with a lifetime of >20 yr. The tubes are packaged in a metal housing and are fitted with single-mode fiber pigtails. All optics are coated and wedged for low backreflection and minimum interference. A built-in InGaAs photodiode can transform the output from optical to electrical. The cells, measuring 2.5 × 0.55 × 0.43 in., can be directly mounted on a circuit board for use in portable instruments. Applications include the characterization of ultradense WDM transmission systems and components, the calibration of optical spectrum analyzers and tunable lasers, and the calibration/verification of optical test equipment.