Performance analysis on an instantaneous microwave frequency measurement with tunable range and resolution based on a single laser source

• Only one CW laser is used as the source and no optical filter is required.
• Tunable range and resolution can be realized by changing incident polarization angle.
• The trade-off problem between measurement range and resolution can be alleviated.
• The bias-drift problem of PolM is proved to have little impact.

A prototype of instantaneous microwave frequency measurement with tunable range and resolution based on a single laser source is proposed and analyzed. In the proposal, one polarization modulator (PolM) followed by a section of dispersion compensating fiber (DCF), a polarization beam splitter (PBS) and two photodiodes (PDs) are used as the key component. To obtain an amplitude comparison function (ACF), the lightwave from a laser source should be first oriented at an angle of α (α≠0° or 90°) relative to one principal axis of PolM. After transmission of DCF, the PBS is connected with principal axis ±45° to that of PolM. Then, by monitoring and processing the microwave power of two optical paths via two PDs, frequency of microwave signal can be easily estimated. It is found that the measurement range can be stretched by simply adjusting α. Its performance is first analyzed by theory and then verified by simulations. Since the proposal is characteristic with its tunable measurement range and resolution, a frequency measurement range as large as 13.2 GHz with a measurement resolution of ±0.15 GHz is obtained.