Abstract: A multi-wavelength light source apparatus includes a tunable light source, optical intensity modulator, optical coupler, annular optical delay circuit, and optical gate device. The tunable light source successively changes and outputs a plurality of output lights different in wavelength from one another. The optical intensity modulator outputs a modulated signal light obtained by modulating an amplitude of the output light outputted from the tunable light source over a predetermined time. The optical coupler is optically connected to the optical intensity modulator, and receives the light outputted from the optical intensity modulator. The annular optical delay circuit is optically connected to the optical coupler, and delays a part of the output light outputted from the optical intensity modulator over a time longer than the predetermined time.

Abstract: The dielectric material includes a pre-baked powder containing Pb(Mg.sub.1/3 Nb.sub.2/3)O.sub.3, BaTiO.sub.3, and BaZrO.sub.3, and lead oxides alone or lead oxides and copper oxides in combination. Thus, the dielectric material is sintered at low temperatures of 800.degree.-1000.degree. C., and makes it possible to use inexpensive electrode materials such as copper, silver, and silver-palladium alloy for the electrode. The dielectric material also makes it possible to produce a ceramic condenser or a thin condenser having a stable capacitance irrespective of changes in temperature.