PM products What is light? Nowadays, our deepest knowledge of Nature: The Standard Model 2 DIAMOND SA 4/1/2019 What is light? Nowadays, our deepest knowledge of Nature: The Standard Model photons φῶς light 3 DIAMOND SA 4/1/2019 What is light? Nowadays, our deepest knowledge of Nature: The Standard Model 4 DIAMOND SA 4/1/2019 What is light? Nowadays, our deepest knowledge of Nature: The Standard Model Light Wave Particles 5 DIAMOND SA 4/1/2019 What is light? Light is (also) a tool Nowadays, our deepest knowledge of Nature: Fastest energy vector The Standard Model • Power transport and conversion • Information technology Interactions with matter • Sensors • Manufacturing • Imaging Light Wave Particles Space and time versatility • From light years to nanometers (10-9 m) • From continuum to attoseconds (10-18 s) 6 DIAMOND SA 4/1/2019 Light as an electromagnetic wave Light 푬 electric field Wave Particles 푯 magnetic field Oscillation of 푬 and 푯 fields 7 DIAMOND SA 4/1/2019 Light as an electromagnetic wave: Oscillation of 퐸 and 퐻 Propagation Amplitude E(t) A A Most of light applications 2 1 푖(푘∙푟−휔푡+휑) rely on a combination of t 퐸 = 퐸0 푒 the wave properties of light. Frequency (or wavelength c = λ ∙ 휈) UV IR 8 DIAMOND SA 4/1/2019 Light as an electromagnetic wave: Oscillation of 퐸 and 퐻 Propagation • Illumination • Imaging and microscopy • LIDAR (Time of flight) • … Amplitude E(t) • Digital data transmission A A • Laser machining Most of light applications Missing2 1 something? Some rely on a combination of t (cutting, welding, etc.) applications are the wave properties of • Laser weapons more focused on light. • … one aspect Frequency (or wavelength λ = 푐 ∙ 휈) • Spectroscopy UV IR • Sensors • Microscopy • Light-matter interaction • … 9 DIAMOND SA 4/1/2019 Polarization Light waves oscillate in a 3D space: 푖(푘∙푟−휔푡+휑) 1D propagation direction 퐸 = 퐸0 푒 2D oscillation plane How is 퐸 oriented in this plane? Polarization Oscillation direction of 퐸 in the plane ┴ to propagation Light can be: Unpolarized 퐸 is the sum of short incoherent wave trains produced independently by a large number of atoms with randomly varying polarization (no stable oscillations in time): Sun light, incandescent lamps, flames etc.. Partially polarized 퐸 is the sum of unpolarized and polarized components: Scattered, reflected or refracted light Polarized 퐸 shows a constant and stable oscillation behavior: Laser light, light passed through a polarizer 10 DIAMOND SA 4/1/2019 Outline Polarization of light PM connectors: assembly • Definitions • Fabrication methods • Polarization states • Standards • Polarization extinction ratio (PER) • Different products • Why is polarization interesting • Connector types Polarization maintaining fibers • Performance • Fiber types Conclusions • Properties • Quality and consequences Measurement techniques • Coherent method • Incoherent method • Setups • Comparison • Connection sequence 11 DIAMOND SA 4/1/2019 Polarization Light waves oscillate in a 3D space: 퐸 = 퐸 푒푖(푘∙푟−휔푡+휑) 1D propagation direction 0 2D oscillation plane How is 퐸 oriented in this plane? Polarization Oscillation direction of 퐸 in the plane ┴ to propagation 12 DIAMOND SA 4/1/2019 Polarization Light waves oscillate in a 3D space: 퐸 = 퐸 푒푖(푘∙푟−휔푡+휑) 1D propagation direction 0 2D oscillation plane How is 퐸 oriented in this plane? Polarization Oscillation direction of 퐸 in the plane ┴ to propagation Polarized light Horizontal Vertical 13 DIAMOND SA 4/1/2019 Polarization y Decomposition of 푬 푬 A 2D vector can always be decomposed in 2 perpendicular components 푬풚 2휋푛푥 퐸 cos 푧 − 휔푡 The polarization state carries x 퐸푥 푥0 휆 퐸 = = information: we can double the 푬풙 퐸 2휋푛푦 푦 퐸 cos 푧 − 휔푡 − 휙 푦0 휆 information content of one wave 14 DIAMOND SA 4/1/2019 Polarization y Circular and elliptical polarizations 푬 Circular P: 푬풙,푬풚 with same amplitude, but with a phase difference (f = 90°) 푬풚 Elliptical P: 푬 ,푬 with ≠ amplitude and/or f ≠ 0°, 90°, 180°, 270° 풙 풚 x 푬 Circular 풙 2휋푛푥 퐸 퐸푥0 cos 푧 − 휔푡 퐸 = 푥 = 휆 퐸 2휋푛푦 푦 퐸 cos 푧 − 휔푡 − 휙 푦0 휆 15 DIAMOND SA 4/1/2019 Polarization extinction ratio (PER) 2휋푛푥 퐸 퐸푥0 cos 푧 − 휔푡 The PER is defined as the ratio between the 퐸 = 푥 = 휆 maximum and the minimum amplitude values 퐸 2휋푛푦 푦 퐸 cos 푧 − 휔푡 − 휙 푦0 휆 assumed by the 퐸 field during one oscillation y period 2 퐸푚푎푥 푃퐸푅 = 2 퐸 풚풐 푚푖푛 푬 x 푬풙풐 16 DIAMOND SA 4/1/2019 Why is polarization interesting? Polarization is crucial in light-matter interaction P must be taken into account or controlled in endless applications in telecom, engineering and sensing: Data transmission and reception Stress induced birefringence Ellispometry Mineralogy Chemistry Astronomy Photography Display technologies Practical examples WDM, including optical modulators, sensors, interferometers. Sensor Measuring Modulators - In various Telecommunication systems around the world Interferometers 17 DIAMOND SA 01/04/2019 Why a PM fiber optic connector? What advantage does a PM fiber optic system grant? PM fiber optic offer a stable state of polarization, Easy analysis of interference of two optical waves. The information encoded in P is preserved The P quality coming from the source is not degraded What are future market prospects? Optical components that rely on a fixed and controlled P state Coherent optical communications (tendency is increasing with modulator technology) Sensing, imaging, diagnostics, birefringence applications and many others What are important parameters of a PM optical connector? Extremely precise axes alignment Low core eccentricity: Consistent, repeatable low insertion loss Stressless fiber High extinction ratio High return loss 18 DIAMOND SA 01/04/2019 Outline Polarization of light PM connectors: assembly • Definitions • Fabrication methods • Polarization states • Standard • Polarization extinction ratio (PER) • Diamond grade • Why is polarization interesting • Comparison and specs Polarization maintaining fibers • Connectors • Tipi di connettori • Fiber types • Limitazioni • Properties • Ordinazioni • Quality and consequences • Prodotti standard Measurement techniques • Prodotti speciali • Coherent method • Incoherent method Conclusions • Setups • Comparison • Connection sequence 19 DIAMOND SA 4/1/2019 PM fibers Polarization maintaining fibres present a structure which allows to certain input polarization states to propagate unchanged 20 DIAMOND SA 4/1/2019 Working principle Break the symmetry! We need to differently modify the refractive indexes along the axis Stress elements cladding core Standard fiber Panda PM fiber ny 푬 ny 푬 refractive indexes nx nx 21 DIAMOND SA 4/1/2019 PM fibers: working principle The different components of the 퐸 field travel at different velocities ny 푬 Speed of light in materials: 푐 푣 = 푛 푬 Therefore: 풚 nx 푛푦 > 푛푥 ⇒ 푣푦 < 푣푥 푬풙 푬풚 will be delayed compared to 푬풙 All polarization states not aligned with the fiber axis will evolve during propagation in a circular or elliptical polarization. Linearly polarized light along the fiber axis will propagate unchanged. 22 DIAMOND SA 4/1/2019 Polarizing fibers (PZ): working principle A PZ fiber is designed so that only one state of polarization is guided along the fiber Any other polarization state will be lost rapidly, thus yielding a high built-in polarization extinction ratio Careful optimization of the glass composition resulting in both high birefringence and leakage behavior Typically based on bow-tie or oval-core structures Different measurement procedures compared to standard PM fibers 23 DIAMOND SA 4/1/2019 Fundamental aspects To preserve the P-state in a good PM fiber: Homogeneous axis orientation all along the fiber Fiber producer (mainly) Great birefringence (short beat length) NO external stress (mechanical and/or thermic) Fiber connectorization (also) Twist stress Curvature stress Compression stress 24 DIAMOND SA 4/1/2019 Outline Polarization of light PM connectors: assembly • Definitions • Fabrication methods • Polarization states • Standard • Polarization extinction ratio (PER) • Diamond grade • Why is polarization interesting • Comparison and specs Polarization maintaining fibers • Connectors • Tipi di connettori • Fiber types • Limitazioni • Properties • Ordinazioni • Quality and consequences • Prodotti standard Measurement techniques • Prodotti speciali • Coherent method • Incoherent method Conclusions • Setups • Comparison • Connection sequence 25 DIAMOND SA 4/1/2019 How to measure polarizations With Polarizer 2휋푛푥 2 퐸 퐸푥0 cos 푧 − 휔푡 • We measure the intensity ( 퐸 ), not the actual field 퐸 퐸 = 푥 = 휆 퐸 2휋푛푦 푦 퐸 cos 푧 − 휔푡 − 휙 • We loose the instantaneous information (we average) 푦0 휆 • Phase (휙) information is missing y With a simple polarizer, it is not possible to unambiguously define a polarization state The results of such a PER measurements can be misinterpreted x 26 DIAMOND SA 4/1/2019 PER measurement: coherent method Goal 2휋푛 퐸 cos 푥 푧 − 휔푡 퐸푥 푥0 휆 Determine the polarization ellipsis 퐸 = = 퐸푦 2휋푛푦 퐸푦0 cos 푧 − 휔푡 − 휙 Determine the ellipsis’ orientation 휆 y Light source E(t) t Monochromatic laser Int. (f) Narrow spectrum f y Good temporal coherence: x Limits the maximal patch cord length polarizer Measurement setup Polarizer to define the initial P-state Polarimeter to analyze the final P-state and hence derive the PER 27 DIAMOND SA 4/1/2019 PER measurement: coherent method Polarization state 퐼0;0 P is derived from four intensity 퐼90;0 measurements 퐼45;0 퐼45;90 Stokes parameters: 푠 퐸2 + 퐸2 0 퐼0;0 푠 + 푠 푠0 푥0 푦0 represents the total intensity 0