  We present photometric and spectroscopic observations of the optical
companion to the millisecond radio pulsar PSR J1740-5340 in the globular
cluster NGC 6397. An analysis of the photometric variability in the B, V, and
I-bands indicates an inclination of the system of 43.9+-2.1 degrees if the
optical companion fills its Roche lobe (a semi-detached configuration). The
spectroscopic data show a radial velocity variation with a semi-amplitude of
K=137.2 +- 2.4 km/sec, and a system velocity gamma=17.6 +- 1.5 km/sec,
consistent with cluster membership. We use these results to derive a mass of
the optical companion of M1=0.296 +- 0.034 Msol and M2=1.53 +- 0.19 Msol for
the pulsar. There is evidence for secular change of the amplitude of the
optical light curve of the variable measured over seven years. The change does
not have interpretation and its presence complicates reliable determination of
the absolute parameters of the binary.
