The Agilent 81642A Tunable Laser Source (TLS) with Option 072 is a precision instrument for C- and L-band optical testing. It delivers mode-hop-free tuning across 1510–1670 nm with 0.1 pm wavelength resolution and ±0.015 nm absolute accuracy. The integrated real-time wavelength meter and built-in wavelength control enable stable, repeatable measurements. Option 072 specifies a Polarization Maintaining Fiber (Panda-type) output with angled contact connector, achieving 60 dB typical return loss and 16 dB extinction ratio to suppress reflections and spectral ripple. Output power reaches +7 dBm maximum, with ±0.01 dB stability. Spectral linewidth measures 100 kHz (coherent control off) or >50 MHz (1520–1620 nm at maximum flat output, coherent control on). The tuning span supports any 50 nm window within 1520–1620 nm at flat output power >2 dBm. Built for DWDM system validation and optical amplifier characterization, the module warms up in <20 minutes and operates across 10–35 °C. GPIB and RS-232C interfaces enable automated test control. The unit fits the bottom slot of 8164A and compatible Agilent 8163A/B, 8164A/B, and 8166A/B mainframes. Factory calibrated; 2-year recalibration interval recommended.