Anritsu Co.'s MS9710C optical spectrum analyzer has been upgraded for accurate L-band measurements for systems with 50-GHz channel spacing. The device offers a dynamic range of 70 dB at 1 nm, optical signal-to-noise ratio of >47 dB and wavelength accuracy of >0.02 nm at the L- and C-bands. It provides linearity of ±0.1 dB from 1520 to 1620 nm, and ±0.05 dB from 1550 to 1600 nm. The analyzer produces 50-pm resolution with accuracy of ±3 percent and optical sensitivity of -90 dBm. Applications include analysis of erbium-doped fiber amplifiers, NF/gain, LD waveforms and polarization mode dispersion.