Managing dispersion affected OCDMA auto-correlation based on PS multi-wavelength code carriers using SOA

Distortion of the OCDMA auto-correlation width by fiber chromatic dispersion can severely influence incoherent OCDMA transmission based on picosecond multi-wavelength pulses. To the best of our knowledge, we report for the first time the use of SOA for manipulation of the OCDMA auto-correlation consisted of multi-wavelength code carriers in order to provide needed compensation. The OCDMA transmission system was based on two- dimensional wavelength-hopping time-spreading (2D-WH/TS) codes with 8 ps multi-wavelength pulses as the code carriers. Different techniques deploying SOA for auto-correlation width adjustment were investigated and their effectiveness was subsequently verified on the OCDMA transmission through a 17 km long fiber optic testbed connecting Strathclyde and Glasgow Universities

The application of SOA for dispersion management of 2D-WH/TS codesin incoherent OCDMA system

In high data rate optical fibre communication networks, dispersion phenomenon plays a pivotal role. It is important to investigate the dispersion effects in a multi-wavelength picosecond optical code division multiple access (OCDMA) system. This research is focused on the analysis of the effects of fibre dispersion on the OCDMA autocorrelation; and how these effects can be resolved in a tuneable way so that the originally recovered OCDMA autocorrelation function at the decoder receiver can be revived without further manual adjustment of fibre (SMF-28) cable lengths.;The environmental effects and the subsequent mitigation process are also investigated further in this research. The chirp in OCDMA is examined experimentally and analytically in an initiative to find the more in-depth understanding of finely tuneable chromatic dispersion (CD) compensation technique in a coarsely compensated link by using semiconductor optical amplifier (SOA). A practical investigation was carried over a partially CD compensated 17 km bidirectional testbed between the University of Strathclyde and the University of Glasgow to perform the fine-tuning of CD adjustment using SOA.;A 19.5 km SMF-28 fibre spool was also used in an environmental chamber to investigate the temperature induced dispersion effects and subsequent mitigation. The tuneable dispersion compensation measures are vital to ensure the high data rate optical communication using an all-optical approach in future data network end-points where the advantages of ultra-high speed optical communication bandwidth are at present disrupted due to opto-electronic conversions commonly known as 'electronic bottlenecks'.In high data rate optical fibre communication networks, dispersion phenomenon plays a pivotal role. It is important to investigate the dispersion effects in a multi-wavelength picosecond optical code division multiple access (OCDMA) system. This research is focused on the analysis of the effects of fibre dispersion on the OCDMA autocorrelation; and how these effects can be resolved in a tuneable way so that the originally recovered OCDMA autocorrelation function at the decoder receiver can be revived without further manual adjustment of fibre (SMF-28) cable lengths.;The environmental effects and the subsequent mitigation process are also investigated further in this research. The chirp in OCDMA is examined experimentally and analytically in an initiative to find the more in-depth understanding of finely tuneable chromatic dispersion (CD) compensation technique in a coarsely compensated link by using semiconductor optical amplifier (SOA). A practical investigation was carried over a partially CD compensated 17 km bidirectional testbed between the University of Strathclyde and the University of Glasgow to perform the fine-tuning of CD adjustment using SOA.;A 19.5 km SMF-28 fibre spool was also used in an environmental chamber to investigate the temperature induced dispersion effects and subsequent mitigation. The tuneable dispersion compensation measures are vital to ensure the high data rate optical communication using an all-optical approach in future data network end-points where the advantages of ultra-high speed optical communication bandwidth are at present disrupted due to opto-electronic conversions commonly known as 'electronic bottlenecks'

Investigation of the impact of fibre impairments and SOA-based devices on 2D-WH/TS OCDMA codes

In seeking efficient last-mile solutions for high-capacity, optical code division multiple access (OCDMA) emerges as a promising alternative high-speed optical network that can securely support a multitude of simultaneous users without requiring extensive equipment. This multiplexing technique has recently been the subject of comprehensive research, highlighting its potential for facilitating high-bandwidth multi-access networking. When contrasted with techniques such as wavelength division multiplexing (WDM) and optical time division multiplexing (OTDM), OCDMA offers a more effective and equitable split of available fibre bandwidth among the users. This thesis presents my research focused on the incoherent OCDMA under the influence of optical fibre impairments that uses picosecond multiwavelength pulses to form two-dimensional wavelength hopping time-spreading (2D-WH/TS) incoherent OCDMA codes. In particular, self-phase modulation, temperature induced fibre dispersion, chromatic dispersion, as well as the impact of semiconductor optical amplifier SOA devices deployment on 2D-WH/TS OCDMA code integrity were investigated. These aspects were investigated using a 17-km long bidirectional fibre link between Strathclyde and Glasgow University. In particular, I investigated the impact of temporal skewing among OCDMA code carriers and the importance of selecting small range of wavelengths as code carriers where wide range manifest high dependency on wavelength. This wavelength dependency is exploited furthermore to measure the induced temperature dispersion coefficient accurately and economically. I have conducted experiments to characterise the impact of SOA-device on 2D OCDMA code carries which is evaluated under different bias conditions. This evaluation addressed the potential challenges and ramifications of the gain recovery time of SOA and its wavelength dependency with respect to gain ratio and self-phase modulation (SPM). The OCDMA code was built using multiplexers and delay lines to create a 2D OCDMA code to allow studying the impact of deploying a SOA under different conditions on each wavelength. The concept described above is then extended to the investigation of the SOA’s impact on a 2D-WH/TS OCDMA prime code under high bias current/gain conditions. The overall performance of two different 2D-WH/TS OCDMA systems deploying the SOA was also calculated. I have also investigated the possibility of manipulating chirp in 2D-WH/TS incoherent OCDMA to counteract the self-phase modulation-induced red shift by using single mode fibre and lithium crystals. I have investigated the performance of the picosecond code based optical signal when subjected to temperature variations similar to that experience by most buried fibre systems. I have proposed and demonstrated a novel technique, which I examined analytically and experimentally, that utilises a SOA at the transmitter to create a new code with a new wavelength hopping and spreading time sequences to achieve a unique physical improved secure incoherent OCDMA communication method. A novel fully automated tuneable compensation testbed is also proposed of an autonomous dispersion management in a WH/TS incoherent OCDMA system. The system proposed manipulates the chirp of OCDMA code carriers to limit chromatic dispersion detrimental effect on transmission systems.In seeking efficient last-mile solutions for high-capacity, optical code division multiple access (OCDMA) emerges as a promising alternative high-speed optical network that can securely support a multitude of simultaneous users without requiring extensive equipment. This multiplexing technique has recently been the subject of comprehensive research, highlighting its potential for facilitating high-bandwidth multi-access networking. When contrasted with techniques such as wavelength division multiplexing (WDM) and optical time division multiplexing (OTDM), OCDMA offers a more effective and equitable split of available fibre bandwidth among the users. This thesis presents my research focused on the incoherent OCDMA under the influence of optical fibre impairments that uses picosecond multiwavelength pulses to form two-dimensional wavelength hopping time-spreading (2D-WH/TS) incoherent OCDMA codes. In particular, self-phase modulation, temperature induced fibre dispersion, chromatic dispersion, as well as the impact of semiconductor optical amplifier SOA devices deployment on 2D-WH/TS OCDMA code integrity were investigated. These aspects were investigated using a 17-km long bidirectional fibre link between Strathclyde and Glasgow University. In particular, I investigated the impact of temporal skewing among OCDMA code carriers and the importance of selecting small range of wavelengths as code carriers where wide range manifest high dependency on wavelength. This wavelength dependency is exploited furthermore to measure the induced temperature dispersion coefficient accurately and economically. I have conducted experiments to characterise the impact of SOA-device on 2D OCDMA code carries which is evaluated under different bias conditions. This evaluation addressed the potential challenges and ramifications of the gain recovery time of SOA and its wavelength dependency with respect to gain ratio and self-phase modulation (SPM). The OCDMA code was built using multiplexers and delay lines to create a 2D OCDMA code to allow studying the impact of deploying a SOA under different conditions on each wavelength. The concept described above is then extended to the investigation of the SOA’s impact on a 2D-WH/TS OCDMA prime code under high bias current/gain conditions. The overall performance of two different 2D-WH/TS OCDMA systems deploying the SOA was also calculated. I have also investigated the possibility of manipulating chirp in 2D-WH/TS incoherent OCDMA to counteract the self-phase modulation-induced red shift by using single mode fibre and lithium crystals. I have investigated the performance of the picosecond code based optical signal when subjected to temperature variations similar to that experience by most buried fibre systems. I have proposed and demonstrated a novel technique, which I examined analytically and experimentally, that utilises a SOA at the transmitter to create a new code with a new wavelength hopping and spreading time sequences to achieve a unique physical improved secure incoherent OCDMA communication method. A novel fully automated tuneable compensation testbed is also proposed of an autonomous dispersion management in a WH/TS incoherent OCDMA system. The system proposed manipulates the chirp of OCDMA code carriers to limit chromatic dispersion detrimental effect on transmission systems