We present preliminary results of 7 years of Arecibo timing of the pulsar-white dwarf binary PSR J1738+0333 .
We can measure the proper motion , parallax with excellent precision and have detected the orbital decay .
Furthermore , the companion has been detected at optical wavelengths and a mass ratio of 8.1 \pm 0.3 has been measured from the orbital variation of its Doppler shift .
Once the companion mass is determined from the optical measurements , this system will provide strong limits for the radiation of dipolar gravitational waves .
Assuming that general relativity holds , the fast-improving measurement of the orbital decay , combined with the measurement of the mass ratio , will provide an independent and precise measurement of the component masses .