Optical Fiber Technology for Space: Challenges of Development and Qualification

Transcription

1 TM-0026-SYS_02_Vorlage Präsentation Hans Thiele, Michael Goepel , ICSO 2014, Tenerife Optical Fiber Technology for Space: Challenges of Development and Qualification

2 Introduction Design, development and qualification of fiber optical subsystems often challenging Translation of system and mission requirements into a dedicated design Availability of qualified COTS components Knowledge of assembly and integration processes gives additional limitations General Problem of Fiber Optics for Space Application: Lack of generic qualification standard for photonic assemblies From the experience from several, a generic development and qualification approach was developed with focus on passive components and assemblies, using COTS parts Page 2

3 General Design and Development Constraints Schedule, Costs Mass limitations Manufacturing process constraints Environmental requirements: Thermal, typically -55 C to +85 C (operational) Radiation, e.g. 2 krad to 100 krad (typically) Vibration & Shock loads Integration requirements and constraints often considered too late Special Mission requirements, like planetary protection Design & Development Identification of Requirements & Constraints Part Selection Failure Mode Identification Selection of Verification Methods Verification & Qualification Plan Design Fiber Batch Acceptance Qualification Testing Flight Model Assembly Manufacturing Page 3

4 Procurement and Qualification General Situation: No general Standard for qualification of optical fiber assemblies for space application is existing Some standards available for components (fiber connectors, active components), but assemblies including optical fibers are still insufficient covered The following generic approach was developed to cover all aspects from the beginning of the flight part procurement, assembly manufacturing to qualification The same batch of optical fiber will be used for all qualification and flight models Dedicated samples are manufactured for qualification testing Tests to be performed with in-situ monitoring of the transmission as far as possible Representative test parameters and test margins have to be defined for the qualification tests Components may only be tested in assembled or mated condition, not as stand-alone part Page 4

5 Procurement and Qualification Design & Development Procurement of Optical Fiber* Cable Assembly Radiation Qualification Tests (TID, Proton) Workmanship Test: Thermal-Cycling *This Fiber Batch will be used for all qualification tests, development & flight models Fiber Batch Acceptance Qualification Sample Manufacturing Cable Thermal Preconditiong Sample Manufacturing / Cable Termination Environment Tests Thermal Testing (Thermal-Cycling, Thermal-Vakuum) Vibration Testing (sinus, random) Shock Testing Qualification Testing Optional or Missionspecific tests E.g. Packaging Tests Outgassing Tests Optional tests as needed Flight Model Assembly Manufacturing Page 5

6 Flight Models Flight samples will be manufactured after qualification testing The same batch of optical fiber will be used for all qualification and flight models Flight parts will undergo acceptance testing with reduced loads compared to qualification testing Approach to be tailored if required, e.g. by introducing additional tests Some additional tests on system / instrument level may be required Qualification Testing Flight Model Assembly Manufacturing Cable Thermal Preconditiong Component Manufacturing / Cable Termination Thermal Acceptance Test Vibration Acceptance Test Delivery & Integration of Flight Hardware Flight HW Page 6

7 Design of the ExoMars RLS Optical Harness For the ExoMars Raman (RLS) instrument, a dedicated optical harness was developed During the course of the project, the requirements baseline was changed several times, which had to be reflected in the selection of the components and test approach The following components are used: Fiber: Multimode, step-index, 50µm core fiber Cable: 1.2mm Gore Simplex MiniAVIM connectors Customized MiniAVIM receptacle MiniAVIM connector Mating adapter Fiber optical cable MiniAVIM receptacle Page 7

8 Verification Identify failure modes for components and assemblies Components may have different failure modes in an assembly (=combination of components) than as stand alone part Select tests to verify the design, cover most failure modes and test components and assembly for workmanship Some components may not be tested as stand alone part tests only representative in an assembly or in mated condition, e.g. most tests with fiber connectors tests only representative in flight configuration, e.g. for some assemblies Dedicated tests for special/customized components may be required Page 8

9 Component Testing & Verification MiniAVIM Connectors Several tests were performed, e.g. Thermal-Cycling tests; range -60 C to +60 C Vibration tests, sinus and random, up to 55g rms Torsion and Cable retention tests Integration Tests Tests were performed with in-situ monitoring Cable assemblies were in a flight representative configuration (same components / cable types, but different batches) Page 9

10 Component Testing & Verification MiniAVIM Receptacle High-precision free space adapter for connection of the optical head and Spectrometer Custom made, high-precision, all-titanium part (no optical parts) Stand-alone tests not possible a connector + fiber would be needed, but this does not tell anything how to distinguish failure modes from the connector Qualification and performance tests have to be performed on instrument level, when the component is integrated in the subsystem Page 10

11 Radiation Testing of Optical Fibers Background Creation of color centers in optical fibers exposed to radiation transmission loss Magnitude of this effect depends on temperature, radiation dose rate, total dose, doping substances of the fiber, and the manufacturing process The drawing process of optical fibers is significant for the number of radiation precursors Each fiber batch is drawn from one individual preform Drawing process of one fiber type might be changed by the manufacturer over time Different batches of one fiber from the same manufacturer might have different radiation response due to changes in the manufacturing process Radiation testing of every flight batch required Page 11

12 Radiation Testing of the ExoMars RLS Fibers Several fiber candidates from different suppliers were chosen during early Phase B of the project in 2008 TID Co-60 and 50 MeV proton irradiation tests were performed to support the selection process the UV50/125P fiber showed the best radiation response However: no funding to procure sufficient fiber from all candidates for qualification and flight models A new batch of the selected UV50/125P fiber was procured A TID Co- 60 Radiation acceptance test was performed in 2014 and compared to the 2008 TID test to compare the radiation response; within the measurment accuracy of the tests, the radiation response was similar Page 12

13 Radiation Testing of the ExoMars RLS Fibers Shielding Fibers under Test Co60- Source Page 13

14 Radiation Induced Attenuation [db/m] Radiation Testing of the ExoMars RLS Fibers Test 658nm 2014 Test 863nm 2008 Test 658nm 2008 Test 863nm TID Co-60 Test on the UV50/125P Optical Fiber Comparision of the 2014 Workmanshiptest to the 2008 Qualification Test TID [krad] Page 14

15 Radiation Testing of Optical Fibers Test Approach Test selection according to mission requirements (TID gamma, proton, etc.) Careful with accelerated testing and safety margins to avoid overtesting! Testing of samples from different vendors helpful for selection, if tests performed in early project stages If qualification tests performed in earlier project phases, only an acceptance test is required to check if the radiation response has changed Using only an TID Co-60 as acceptance test is sufficient, if qualification test on the same fiber type in representative radiation environment was already performed complete qualification test data is available and all test conditions are known (e.g. dose rate) radiation response is same or better than observed during earlier qualification tests Page 15

16 Summary and Outlook This talk gave a short overview of the challenges of the development, verification and qualification of fiber optical components and subsystems for space application Using the experience from several projects, a generic development and qualification approach was developed, which is presented here Focus on Radiation testing of optical fibers: acceptance tests have to be conducted for every flight batch due to the large role of the manufacturing process This approach is currently the baseline for the qualification approach on the optical harness for the ExoMars Raman spectrometer, which is targeted to be launched in 2018 Page 16

17 Acknowledgements Part of this work has been carried out within the Raman Laser Spectrometer instrument development and we thank our science and industrial partners for their collaboration. Activities at Kayser-Threde were performed under contract with University of Jena, Institute for Physical Chemistry, kindly funded by the German Space Agency DLR within the ExoMars Raman instrument activities. Special thanks go to Frederic Taugwalder at Diamond S.A. and Jochen Kuhnhenn at Fraunhofer INT. Page 17