© 2005, it - instituto de telecomunicações. Todos os direitos reservados. This tutorial is licensed under the Creative Commons Coordinator: António Teixeira, Co-Coordinator: K. Heggarty António Teixeira, Paulo André, Rogério Nogueira, Tiago Silveira, Ana Ferreira, Mário Lima, Ferreira da Rocha, J. Prat, J. A. Lazaro, C. Bock, J. Andrade 2B- Optical Technologies E-Photon One Curriculum

2 E1- 2b Optical technologies Jan 2006 Program 1. Basic Photonic Measurements 2. Material growth and processing 3. Semiconductor materials 4. Transmission systems performance assessment tools 5. Optical Amplifiers a)Semiconductor Optical Amplifiers (SOAs) b)Erbium Doped Fiber Amplifiers (EDFAs) c)Fiber Amplifiers- Raman d)Other Amplifiers 6. Emitters a)Semiconductor b)Fiber 7. Receivers a)PIN b)APD 8.Modulators a)Mach Zehnder b)Electro-absorption c)Acoust-optic 9.Filters a)Fiber Bragg gratings b)Fabry Perot c)Mach-Zehnder 10.Isolators 11.Couplers 12.Switches a)Mechanical b)Wavelength converters c)Multiplexers/ Demultiplexers

© 2005, it - instituto de telecomunicações. Todos os direitos reservados. This tutorial is licensed under the Creative Commons Basic Photonic Measurements Paulo André, António Teixeira, J. Prat, J. A. Lazaro, C. Bock

4 1. Basic photonic measurementsBasic photonic measurements 1. Optical Signal CharacteristicsOptical Signal Characteristics 1.1. Energy (1)Energy 1.2. Coherence (1)Coherence 1.3. Wave (1)Wave 1.4. Wavelength (1)Wavelength 1.5. Frequency (1)Frequency 2. Optical Signal MeasuringOptical Signal Measuring 2.1. Light units (1)Light units 2.2. Optical Spectrum Analyzer (7)Optical Spectrum Analyzer 2.3. Optical Signal to Noise Ratio (1)Optical Signal to Noise Ratio 2.4. Power meter (1)Power meter 2.5. Power and Security (1)Power and Security 2.6. Attenuation (1)Attenuation 2.7. Insertion and Reflection loss (3)Insertion and Reflection loss 2.8. Other Loss Measurements (3)Other Loss Measurements 2.9. Wavelength meter (1)Wavelength meter E1- 2b Optical technologies

5 1. Basic photonic measurementsBasic photonic measurements Reflections OTDR (3)Reflections OTDR Optical Component Analyzer (7)Optical Component Analyzer Optical Power and Chirp (3)Optical Power and Chirp Security - standard (3)Security - standard Bibliography External Modulation (1)External Modulation Optical Amplification (1)Optical Amplification E1- 2b Optical technologies

6 Optical Signal Characteristics - Energy E1- 2b Optical technologies

7 Optical Signal Characteristics - Coherence Coherent Light Photons have a fixed phase relation (laser light) Uncoherent light Photons have a random phase relation (sun, lightbulbs) Coherence length (CL) Average length over which photons loose the phase relation. 1/e 1 CL E1- 2b Optical technologies

8 Optical Signal Characteristics - Wave E1- 2b Optical technologies

9 Optical Signal Characteristics - Wavelength Band O (Original)1260 nm to 1360 nm; Band E (Extended)1360 nm to 1460 nm; Band S (Short wavelength)1460 nm to 1530 nm; Band C (Conventional)1530 nm to 1565 nm; Band L (Long wavelength)1565 nm to 1625 nm; Band U (Ultra-long wavelenth)1625 nm to 1675 nm. E1- 2b Optical technologies

10 Near infrared Frequency Wavelength µm UV (vacuum) 1.2 THz Longhaul Telecom Regional Telecom Local Area Networks 850 nm 1550 nm 1310 nm CD 780 nm HeNe Lasers 633 nm Optical Signal Characteristics – Wavelength ↔ Frequency E1- 2b Optical technologies

11 Optical Signal Measuring - Light Units Light flux (lumen, lm) - power (W) emitted over the visible radiation spectrum. 1 light-watt at 555 nm = 683 lm. Light intensity (candel, cd) – Light flux emitted per solid angle unit. llluminance (lux, lx=lm/m 2 ) – Received luminous flux (per surface). Luminance (L, cd/m 2 ) – Ratio between the light intensity and the surface seen by the human eye in a determined direction. E1- 2b Optical technologies

12 Optical Signal Measuring - Optical spectrum analyser Based on a movable diffraction bragg grating and monochannel detectors OR fixed bragg gratings and CCD E1- 2b Optical technologies

13 Optical Signal Measuring - Optical spectrum analyser E1- 2b Optical technologies

14 Area of mW nm Resolution of 0.05 nm Power = mW Optical Signal Measuring - Optical spectrum analyser- Power E1- 2b Optical technologies

15 Optical Signal Measuring - Optical spectrum analyser- Resolution Resolution of 39 MHz E1- 2b Optical technologies

16 Resolution of 125 MHz Optical Signal Measuring - Optical spectrum analyser- Resolution E1- 2b Optical technologies

17 Resolution of 1250 MHz Optical Signal Measuring - Optical spectrum analyser- Resolution E1- 2b Optical technologies

18 Resolution of MHz Optical Signal Measuring - Optical spectrum analyser- Resolution E1- 2b Optical technologies

19 Optical Signal to noise ratio  Power (W) of the channel divided by the interpolation of the noise.  To get the channel power, the noise power at that wavelength should be removed.  Should be specified for a determined measuring position, Br, usually 0.1 nm, 0.8 nm, 1 nm OR, for WDM systems, half the spacing between channels.  Should be specified for a given resolution, Bm, usually 0.1 nm. Optical Signal Measuring - OSNR E1- 2b Optical technologies

20 Optical Signal Measuring – Power meter Detectors based on PINs, dully callibrated. Dennis Derickson, “Fiber Optic Test and Measurement”, Prentice Hall PTR,1998 E1- 2b Optical technologies

21 Optical Signal Measuring – Typical Values - Security Standards Power (P): Emitter: typical -6 to +17 dBm (0.25 mW to 50 mW) Receiver: typical -3 to -35 dBm (500 µW to 0.3 µW) Amplifiers: typical +3 to +20 dBm (2mW to 100mW) Security Standards International Standard : IEC and E1- 2b Optical technologies

22 Optical Signal Measuring - Attenuation E1- 2b Optical technologies

23 Measurement of insertion losses as a function of the wavelength Tunable spectrum (Laser) Large spectrum (Power meter) Large spectrum (ELED, ASE)Tunable spectrum (OSA) Tunable spectrum (Laser)Tunable spectrum (OSA) Optical Signal Measuring– Insertion loss E1- 2b Optical technologies

24 Optical Signal Measuring– Insertion Loss/Reflection Loss E1- 2b Optical technologies

25 Optical Signal Measuring – Insertion Loss E1- 2b Optical technologies

26 PDL – Polarization Dependent Loss: Maximum change in the insertion loss when the polarization is changed. Laser PolariserPower meter Optical Signal Measuring– Polarization Dependent Loss E1- 2b Optical technologies

27 Optical Signal Measuring – return loss Return loss = PrPr PiPi P r P i E1- 2b Optical technologies

28 RL=14.7 dB Optical Signal Measuring – Coupling Loss E1- 2b Optical technologies

29 Optical Signal Measuring – Wavelength Meter Based on the Michelson interferometer The distance between fringes is proportional to the wavelength E1- 2b Optical technologies

30 A optical pulse is fed into the optical fiber (on one side access). A returning signal is analysed in time and amplitude ( the OTDR shows the relative power of the returning signal versus the distance). we can determine: distance : failure localization, splices, connectors, length of the fiber; losses : in a splice, connector or line; attenuation : comes from the fiber; reflection : in a connector, In mechanical connections (“return-loss”). Optical Signal Measuring – Reflections - OTDR Optical Time Domain Reflectometry E1- 2b Optical technologies

31 Occurrence: - No reflection: Fiber splice; micro curvature; End of fiber. - With reflection (broken fiber): connector / couple of connector; Mechanical connections; Broken Fibre; End of fiber (fiber cut) Optical Signal Measuring – Reflections - OTDR CALIBRATED SCALE, dB E1- 2b Optical technologies

32 Optical Signal Measuring – reflections - OTDR Performance Measurements - Dynamic range dB difference from the initial level of backscattering and the noise; Determination of the maximum distance to be measured - Dead Zone Distance in the initial zone of the fiber for which the OTDR is “blind” by the saturation of the received due to the reflections (e.g.: initial connector); Similarly related to the resolutions of two neighboring occurrences. - Precision in the determination of the range depends on the absolute knowledge of the refraction index. E1- 2b Optical technologies

33  allows the determination of the tranfer function of a device as a function of the wavelength  Determined, usually: insertion losses, group delay, dispersion, PMD and PDL. Optical Signal Measuring – Optical Component Analyser E1- 2b Optical technologies

34 Optical Signal Measuring – Optical Component Analyser E1- 2b Optical technologies

35 Optical Signal Measuring – Optical component analyser E1- 2b Optical technologies

36 Optical fibers Narrow filters Frequency modulation Step Optical Signal Measuring – Modulation frequency vs resolution For greater probe’s modulation frequency, better resolution. E1- 2b Optical technologies

37 Optical Signal Measuring – Optical component analyser - Resolution Error E1- 2b Optical technologies

38 Optical Signal Measuring– Optical Component Analyser- Resolution Spectral Resolution (pm) Modulation Frequency (GHz) Group-Delay Noise (ps) (4 σ ) E1- 2b Optical technologies

39 Optical Signal Measuring– Optical component analyser Group-delay (ps)Wavelength (nm) Chromatic Dispersion (ps/nm) E1- 2b Optical technologies

40 Basic Photonic Measurements - Optical Power Ô Optical Power Measuring : The optical power can be measured in terms of. its average –Eg Optical power meter Hand held, Benchtop –Optical Spectrum Analyser »Wavelength dependent Narrow bandwidth (0.1nm~50nm) E1- 2b Optical technologies

41 Basic Photonic Measurements – Optical Power. Of its time dependent behavior –Oscilloscopes with optical heads or connected to Photodiode »Ps range –Streak Camera »100’s fs range –Auto correlator »fs range E1- 2b Optical technologies

42 Basic Photonic Measurements – Optical chirp Ô Chirp Measuring : Optical Discriminator. optical filters, interferometers (Mach Zehnder, etc), or even heterodyne techniques E1- 2b Optical technologies

43 Security - standard IEC and nm Risk level 1 = 10 mW Risk level 3A = 50 mW Risk level k  3A = 54 mW Risk level 3B = 500 mW Direct observation at the output of a monomode step index fiber at a distance of 100mm and without automatic power control Security in laser products - Part 2: Security in optical communication systems (IEC :2000), NP EN E1- 2b Optical technologies

44 Security - standard IEC and Risk levelType of location FreeRestrictControled 1 No requirements 2 - Labeling - Level 1* departing from the connector or tool needed to disconnect Labeling 3ª - Labeling - Level 1* departing from the connector or tool to disconnect Labeling k  3ª Not allowed ** - Labeling - Protected cables - Level 3A * departing from the connector or tool required for disconnecting Labeling 3B Not allowed ** - Labeling e - Protected cables - Level k* 3A * departing from the connector or tool required for disconnecting 4 Not allowed ** E1- 2b Optical technologies

45 Security - standard IEC and Location with controlled access location where the protection place (confinement) is controlled and only accessible by authorized and trained personnel to deal with laser radiation and inspection of the system. E.g., cable tubes of optical fibre and switching systems Location with restricted access location, where the protection place (confinement) is restricted and locked to the public. E.g., industrial and commercial buildings Location with free access. location, where the access to the protection place (confinement) is free. For example, domestic installations and buildings opened to the public. E1- 2b Optical technologies

46 Bibliography E1- 2b Optical technologies

47 Optical Signal Characteristics- External Modulation  Based on non-linear effects on LiNbO 3 lasers  Require polarization controllers;  Allow input optical powers to 50 mW;  Tipical Insertion Losses of 3 dB;  Vπ of approximately 3.5 V. E1- 2b Optical technologies

48 Optical Signal Characteristics - Optical Amplification Erbium Transference Energy between a pumped signal (980 nm or 1480 nm) 35 dB Gain; Saturation Power of 17 dBm, 30 dBm and 33 dBm.  = 7 µs  = 9 ms E1- 2b Optical technologies

© 2005, it - instituto de telecomunicações. Todos os direitos reservados. This tutorial is licensed under the Creative Commons Practice 1 Characterization of Optical Fibers and Optical Power Splitters P1 - A. Lazaro, C. Bock

50 P1: Fiber alignment Objective: characterization of the core diameter and of the Numerical Aperture Method : measurement of the attenuation as a function of X, (Y,) Z displacements E1- 2b Optical technologies

51 P1: Fiber alignment Take off the lower 5% (consider zero at -13dB), in order to reduce the error due to cladding propagation modes AN = sen(θ) E1- 2b Optical technologies

52 P1: Return loss measurement E1- 2b Optical technologies

© 2005, it - instituto de telecomunicações. Todos os direitos reservados. This tutorial is licensed under the Creative Commons Practice 2 Link characterization with OTDR P2 - A. Lazaro, C. Bock

54 P2: Link characterization with OTDR OTDR: (Optical Time Domain Reflectometer) E1- 2b Optical technologies

55 P2: Link characterization with OTDR  OTDR instrument scheme  Basic principles Rayleigh scattering Events  Performance and operation Dynamic Range Dead-zone Distance accuracy Launch Cord  “OTDR Gainers” E1- 2b Optical technologies

56 P2: OTDR Block Diagram E1- 2b Optical technologies

57 P2: OTDR Basic Principles  Propagation medium changes produce partial reflection of propagating beams. (e.g.: at fiber-air-fiber discontinuities, by Fresnel reflection)  It produces a pulse propagating back to the OTDR => shown as a peak at the trace and registered at the events list. R = E1- 2b Optical technologies

58 P2: OTDR Basic Principles  Rayleigh scattering diffuse light  A part of it will counter-propagate  Rayleigh scattering is the main limit of the optical fiber loss E1- 2b Optical technologies

59 P2: OTDR and Attenuation The OTDR detects a small part of the back propagating Rayleigh scattered signal. It produces linear traces with a slope 2 x the Attenuation of the fiber (the instruments provide compensation). P2: OTDR – Reflective Events Connectors, mechanical splices, fiber fissures produce reflective events (and losses). E1- 2b Optical technologies

60 P2: OTDR – Non-Reflective Events Fusion splices and fiber bends produce local losses, although no reflections. P2: OTDR – Fiber-end A fiber-end can be detected as either a reflective or a non-reflective event. E1- 2b Optical technologies

61 P2: OTDR – Dynamic Range Applied to OTDR, it is the range of the input back-scattered or reflected signal that the OTDR can process without (maximum) overflow over the mean value of the noise level (e.g. 30 dB). It determines the maximum link length and the accuracy of the measurements P2: OTDR – Dead-zone The dead-zone is related with the capability of the OTDR to resolve two close events. The dead-zone of event: corresponds to the optical pulse width (e.g. > 3 meter). The dead-zone of attenuation. Transitory effects avoid proper attenuation measurement (e.g. > 20 meters). E1- 2b Optical technologies

62 P2: OTDR – Dynamic Range vs Dead-zone Dynamic Range depends on: Pulse width Averaging time OTDR design Dead-zone depends on: Pulse width Return loss magnitude OTDR design E1- 2b Optical technologies P2: OTDR – Distance Accuracy Depends on: Clock accuracy Sampling time of the A/D converter Refractive index ( Distance = time*c / n eff ) Cabling factor

63 P2: OTDR – “Gain”?  There is an apparent power increase seen when attempting to measure splice loss with an OTDR  It happens when the amount of backscattered light before the splice is greater than that after the splice or vice-versa  Telecommunications Industry Association fiber optical test procedure (TIA-FOTP-61) indicates that splice loss measurements with an OTDR must be conducted from both directions and averaged for accurate results E1- 2b Optical technologies

© 2005, it - instituto de telecomunicações. Todos os direitos reservados. This tutorial is licensed under the Creative Commons Practice 3 LED and LASER Control P4 - J. Prat, A. Lazaro, C. Bock

65 P3: LED and LASER control  LED Compensation E1- 2b Optical technologies

66 P3: LED and LASER control  LASER control E1- 2b Optical technologies

67 P3: Optical Spectrum Analyzer (OSA)  Spectrum properties’ characterization of the optical source  Typical Working Principle E1- 2b Optical technologies

68 P3: OSA - Applications  Applications LASER characterization Optical channel analysis OSNR measurement E1- 2b Optical technologies