2.48832 GHz SMD-VCXO for OC-768

This paper describes 2.48832 GHz SMD-VCXO used for the SONET OC-768 (40 Gbps) system. The telecommunications provider is advancing in the direction where the OC-768 transmission technology is adopted for the next generation type system like metropolitan area network (MAN) to meet demand for the increasing internet and the multimedia data. The input of 16 signals of 2.5 Gbps is multiplexed in the OC-768 system, and it is assumed one serial 40 Gbps output data stream. The voltage control type oscillator for the reference signal source of PLL circuit for the OC-768 system requires the low sub-harmonics and the phase noise. In this oscillator, 155.52 MHz fundamental mode AT-cut crystal unit is used. The 16/sup th/ higher harmonic signal of 155.52 MHz is selected with 2.48832 GHz SAW filter and amplified. Two stages of this filtering circuit are used to suppress the sub-harmonics effectively. It performs the maximum sub-harmonic level -68 dB, the phase noise -130.34 dBc/Hz@30 kHz. The package size is 40/spl times/12.5/spl times/3.6 mm/sup 3/.