Spectratime mRO-50
2.3.2 Temperature controllers
Since the temperature of the VCSEL and the Cell must be adjusted independently, two separated heaters are necessary
to control the temperature of the PP main parts. The temperatures are controlled by compensating thermal losses using
heating elements (no cooling). Temperature regulation servo-loops are based on a temperature sensor (NTC within a
Wheatstone bridge), Proportional-Integral (PI) regulator and a heating element.
2.3.3 C-field
A pair of C-field coils inside the PP generate a magnetic field which separates the rubidium spectral lines. This magnetic
field allows fine-tuning of the output frequency by shifting the rubidium resonance frequency by the second-order
Zeeman effect.
A stabilized current drives the coils. The current is adjustable for fine-tuning of the output frequency and can be set by a
software interface or by an analog voltage applied to the mRO pin #1.
2.3.4 Telemetries
The user can access these data from a software GUI shown in Figure 5. Telemetry parameters shown include:
• Error signal of the atomic lock loop
• DC signal on photodiode
• VCSEL temperature
• Control signal of the VCSEL temperature controller
• Cell temperature
• Control signal of the Cell temperature controller
• EP temperature
• VCSEL driving current
• Voltage across the VCSEL
• Control voltage of the 10 MHz crystal
Figure 4: Atomic resonance:
error signal detection
