Single-end reflectometric measurements of polarization-mode dispersion in single-mode optical fibres
- Authors: Fosuhene, Samuel Kofi
- Date: 2013
- Subjects: Fiber optics , Polarization (Light) , Optical measurements
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/6280 , vital:21069
- Description: In this thesis two novel single-end methods are applied to measure and characterize polarization mode dispersion in single mode optical fibres. Polarization mode dispersion (PMD) is an important factor negatively affecting the successful implementation of high speed long haul optical fibre networks operating at bit rates of 10Gb/s and above. PMD measurements are thus important for quality control during manufacturing and cabling processes. It is also useful for network operators planning to upgrade bitrates in existing networks to 10Gb/s and beyond. In an optical fibre link, sections with particularly high PMD may act to increase the entire PMD of the link. Identifying and replacing such sections can greatly reduce the PMD of the link. PMD measurements can be forward or single-end. In forward measurements, both ends of the fibre are used for input and detection. In single-end configuration, only one end of the fibre is used. For this reason, single-end measurements are more practical for the field where fibre ends are situated several kilometres apart. Single-end techniques can be implemented with a continuous wave for non-local PMD measurements (by Fresnel reflection). If a pulsed wave is used, local measurements can be achieved (by total power due to Rayleigh scattering). Two single-end schemes, one based on Fresnel reflection and the other due to Rayleigh scattering have been applied to measure non-local and local PMD of standard single mode optical fibres. For the non-local PMD measurements, the general interferometric technique (GINTY) was modified to operate in a round-trip configuration. In this configuration, the fibre was treated as a concatenation of two identical fibre segments. Three different sets of fibres were investigated, each set representing a particular mode coupling regime. For polarization maintaining fibres, (PMFs), with no mode coupling, a factor of two was found between forward and single-end measurements. For long single mode fibres in the long length regime, the factor was 1.4. For a combination of PMF and single mode fibres, a factor of 1.6 was obtained. The method which is accurate, repeatable, low cost and robust is very suitable for field applications. The second method is the polarization optical time domain reflectometric (P-OTDR) technique. This technique performs local birefringence measurements by measuring the evolution of the states of polarization (SOP). The birefringence information from such measurements was extracted and analysed to characterise four different fibres. Beat lengths and correlation lengths extracted from the P-OTDR were used to calculate the differential group delay (DGD) of the fibres. Next an expression for the root-mean-square differential group delay was derived and applied to the birefringence measurements to calculate the DGDs at a single wavelength. This method which operates at a single wavelength has a huge advantage. Firstly it is able to measure completely all the fibre characteristic parameters. Secondly it can measure mean DGD, root mean square DGD and instantaneous DGD. A plot of instantaneous DGD vs. length enables one to identify and eliminate sections with particularly high DGD. Finally since the P-OTDR system operates with a single wavelength, real time monitoring of PMD is possible via multiplexing. The results obtained are repeatable, accurate and are in good agreement with the standard Jones Matrix Eigenanalysis (JME) technique.
- Full Text:
- Date Issued: 2013
Single-end reflectometric measurements of polarization-mode dispersion in single-mode optical fibres
- Authors: Fosuhene, Samuel Kofi
- Date: 2013
- Subjects: Fiber optics , Polarization (Light) , Optical measurements
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/6280 , vital:21069
- Description: In this thesis two novel single-end methods are applied to measure and characterize polarization mode dispersion in single mode optical fibres. Polarization mode dispersion (PMD) is an important factor negatively affecting the successful implementation of high speed long haul optical fibre networks operating at bit rates of 10Gb/s and above. PMD measurements are thus important for quality control during manufacturing and cabling processes. It is also useful for network operators planning to upgrade bitrates in existing networks to 10Gb/s and beyond. In an optical fibre link, sections with particularly high PMD may act to increase the entire PMD of the link. Identifying and replacing such sections can greatly reduce the PMD of the link. PMD measurements can be forward or single-end. In forward measurements, both ends of the fibre are used for input and detection. In single-end configuration, only one end of the fibre is used. For this reason, single-end measurements are more practical for the field where fibre ends are situated several kilometres apart. Single-end techniques can be implemented with a continuous wave for non-local PMD measurements (by Fresnel reflection). If a pulsed wave is used, local measurements can be achieved (by total power due to Rayleigh scattering). Two single-end schemes, one based on Fresnel reflection and the other due to Rayleigh scattering have been applied to measure non-local and local PMD of standard single mode optical fibres. For the non-local PMD measurements, the general interferometric technique (GINTY) was modified to operate in a round-trip configuration. In this configuration, the fibre was treated as a concatenation of two identical fibre segments. Three different sets of fibres were investigated, each set representing a particular mode coupling regime. For polarization maintaining fibres, (PMFs), with no mode coupling, a factor of two was found between forward and single-end measurements. For long single mode fibres in the long length regime, the factor was 1.4. For a combination of PMF and single mode fibres, a factor of 1.6 was obtained. The method which is accurate, repeatable, low cost and robust is very suitable for field applications. The second method is the polarization optical time domain reflectometric (P-OTDR) technique. This technique performs local birefringence measurements by measuring the evolution of the states of polarization (SOP). The birefringence information from such measurements was extracted and analysed to characterise four different fibres. Beat lengths and correlation lengths extracted from the P-OTDR were used to calculate the differential group delay (DGD) of the fibres. Next an expression for the root-mean-square differential group delay was derived and applied to the birefringence measurements to calculate the DGDs at a single wavelength. This method which operates at a single wavelength has a huge advantage. Firstly it is able to measure completely all the fibre characteristic parameters. Secondly it can measure mean DGD, root mean square DGD and instantaneous DGD. A plot of instantaneous DGD vs. length enables one to identify and eliminate sections with particularly high DGD. Finally since the P-OTDR system operates with a single wavelength, real time monitoring of PMD is possible via multiplexing. The results obtained are repeatable, accurate and are in good agreement with the standard Jones Matrix Eigenanalysis (JME) technique.
- Full Text:
- Date Issued: 2013
Development of flexible automotive measurement adaptors for the PQ25 VWSA platform
- Authors: Pretorius, Shaun
- Date: 2009
- Subjects: Automobiles -- Measurement , Optical measurements
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:9626 , http://hdl.handle.net/10948/1632 , http://hdl.handle.net/10948/d1011725 , Automobiles -- Measurement , Optical measurements
- Description: The following work describes all knowledge required in the creation of new automotive optical Photogrammetrical adaptors, which allow the user thereof to measure a fully assembled vehicle in its natural position, i.e. on its wheels for the PQ25 platform at Volkswagen of South Africa. The system is the only method available to the manufacturing plant to measure a fully assembled vehicle in this manner. The FlexMess system allows for a quick portable measurement of a vehicle at all stages of Vehicle manufacturing, aligned via the Volkswagen RPS standards. In the first part of the work, the problem of establishing a system capable of measuring the PQ25 platform is achieved by redesigning the PQ24 platform (previous generation Polo) to the new PQ25 vehicle platform. Once the system was redesigned a prototype adaptor system was created. In the second part of the work, the redesigned adaptor system is checked for its accuracy and repeatability. In a statistical analysis of the adaptors ability to measure the reference points needed for alignment of a vehicle, the system is compared to a CMM and verified that the limits fall within the limits of the original FlexMesśs certified accuracy limits. The last part of the work looks at addressing some of the problems of the FlexMess system by creating concepts for an ideal future FlexMess adaptor system.
- Full Text:
- Date Issued: 2009
- Authors: Pretorius, Shaun
- Date: 2009
- Subjects: Automobiles -- Measurement , Optical measurements
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:9626 , http://hdl.handle.net/10948/1632 , http://hdl.handle.net/10948/d1011725 , Automobiles -- Measurement , Optical measurements
- Description: The following work describes all knowledge required in the creation of new automotive optical Photogrammetrical adaptors, which allow the user thereof to measure a fully assembled vehicle in its natural position, i.e. on its wheels for the PQ25 platform at Volkswagen of South Africa. The system is the only method available to the manufacturing plant to measure a fully assembled vehicle in this manner. The FlexMess system allows for a quick portable measurement of a vehicle at all stages of Vehicle manufacturing, aligned via the Volkswagen RPS standards. In the first part of the work, the problem of establishing a system capable of measuring the PQ25 platform is achieved by redesigning the PQ24 platform (previous generation Polo) to the new PQ25 vehicle platform. Once the system was redesigned a prototype adaptor system was created. In the second part of the work, the redesigned adaptor system is checked for its accuracy and repeatability. In a statistical analysis of the adaptors ability to measure the reference points needed for alignment of a vehicle, the system is compared to a CMM and verified that the limits fall within the limits of the original FlexMesśs certified accuracy limits. The last part of the work looks at addressing some of the problems of the FlexMess system by creating concepts for an ideal future FlexMess adaptor system.
- Full Text:
- Date Issued: 2009
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