SPIE, PA-IVKrzysztof Czuba1 Improved fiber-optic link for the phase reference distribution system for the TESLA technology based projects Krzysztof Czuba ISE, Warszawa, Matthias Felber DESY, Hamburg,

SPIE, PA-IVKrzysztof Czuba2 OUTLINE Design requirements System concept First system version - summary Improvements – second system version Measurement results

SPIE, PA-IVKrzysztof Czuba3 DESIGN REQUIREMENTS Synchronize RF devices located along the accelerator with timing jitter (phase) error << 1 ps Distribution distance: -300 m UVFEL -3.1 km XFEL -15 km ILC Distributed RF signal frequency range: 1 MHz to GHz 1.3 GHz

SPIE, PA-IVKrzysztof Czuba4 LONG TERM PHASE DRIFTS ~ Target Device Drifts caused mainly by temperature changes Electrical / optical length change Reason of drifts: - In fiber: n eff change - In cable: physical dimension and dielectric properties change RF signal source 1.3 GHz signal phase change in 5km of fiber. 10 o C temperature change GHz corresponds to ~2800 ps!! Feedback on phase required!!

SPIE, PA-IVKrzysztof Czuba5 SYSTEM CONCEPT Phase stable signal distribution over long distances (up to 20 km) Feedback on phase suppressing long term drifts Main application of this system is long term phase drifts monitoring / compensation Circulator Long Link Simulator Mirror RF Phase Detector DFB Laser FO Tx FO Rx A Phase Shifter Controller Directional Coupler FO Rx B RF Signal in RF Phase Detector 5 km of single mode fiber in temperature controlled oven Temperature variation Error voltage Output phase check Test system block diagram

SPIE, PA-IVKrzysztof Czuba6 FIRST SYSTEM TEST IN A CLIMATE CHAMBER FIRST EXPERIMENT 1.3 GHz signal source Optical phase shifter (oven with 5km of fiber) Long link simulator (oven with 20km of fiber) RF phase detectors DFB laser F.O. receivers F.O. components (circulator, coupler and other) RF amplifiers Spool with fiber as a phase shifter Problems with cabling, vibration and noise Very slow phase shifter response Closed loop - output signal phase Obtained phase stability: - Short term (1 min): 0.8 ps p-p - Long term : 5 ps p-p System can cover very long distribution distances, up to 20km

SPIE, PA-IVKrzysztof Czuba7 SECOND SYSTEM VERSION - ODL Motorized Optical Delay Line: - Phase shift of 160 o at 1.3 GHz – can cover distribution distances up to 500 m -4.7 fs phase change resolution! - Fast response – possible higher gains in the feedback loop - Digitally controlled – no problems with noise and ambient temperature - Much smaller than the spool inside of the oven

SPIE, PA-IVKrzysztof Czuba8 FIBER-OPTIC BOARD, SYSTEM CRATE All components installed on soft foam base Vibration problems removed Easier to handle Shorter connections, semi-rigid for RF signals Improved power supply distribution Shielding System noise reduced significantly

SPIE, PA-IVKrzysztof Czuba9 NEW PHASE DETECTOR, CONTROLLER GUI Very low sensitivity to ambient temperature changes: 0.01 o / o C Improved interface New functionalities, e.g. automatic measurement data storage and labeling Several important “bugs” removed

SPIE, PA-IVKrzysztof Czuba10 F.O. LINK V.2 – MEASUREMENT RESULTS Measurement performed inside of the climate chamber 5 km of fiber used as long link 100 h measurement duration ODL position followed temperature induced phase drifts Output signal phase significantly more stable than in the first system version because of higher feedback loop gain and faster phase shifter

SPIE, PA-IVKrzysztof Czuba11 SUMMARY Phase shifter Short term stability [ps] Long term stability [ps] spool with fiber, 5km 0.85 ODL Two system versions tested Significant performance improvements obtained by use of the ODL and proper development of system hardware Result comparison Third system generation is under development. Phase shifter made of the ODL and a spool of fiber connected in series. This will allow to use advantages of both solutions