Gain equalization of erbium doped fibre amplifiers with tuneable long-period gratings
- Authors: Nhlapo, Thabiso J.
- Date: 2009-02-26T12:21:27Z
- Subjects: Optical amplifiers , Optical fibers , Optical communications
- Type: Thesis
- Identifier: http://ujcontent.uj.ac.za8080/10210/391229 , uj:8171 , http://hdl.handle.net/10210/2176
- Description: M.Ing. , This thesis is about the gain equalization of erbium doped fibre amplifiers (EDFA), which is a key technology for enabling wavelength-division multiplexed (WDM) optical communication systems. In order to flatten dynamically the EDFA gain spectrum, a tuneable long-period grating filter was demonstrated. Long-period gratings were fabricated by using a KrF excimer laser combined with the metal amplitude mask technique. The transmission spectrum characteristic of the long- period grating was simulated theoretically by the coupled-mode theory. The coupling between the core and cladding modes of the long-period grating was investigated both experimentally and theoretically. The EDFA was constructed by using the forward pumping configuration consisting of pump laser source, WDM couplers, an optical isolator, and the erbium-doped fibre. The EDFA was characterized theoretically and experimentally for WDM applications. The tuneable long-period grating filter design is based on the tuneable coupler that uses the Mach-Zehnder interferometer configuration. The tuneable filter was demonstrated by equalizing the EDFA gain spectrum and the amplified spontaneous emission (ASE) source. The main advantage of this filter compared to other optical filters is its tuneability of the attenuation over a wide range of pump power.
- Full Text:
- Authors: Nhlapo, Thabiso J.
- Date: 2009-02-26T12:21:27Z
- Subjects: Optical amplifiers , Optical fibers , Optical communications
- Type: Thesis
- Identifier: http://ujcontent.uj.ac.za8080/10210/391229 , uj:8171 , http://hdl.handle.net/10210/2176
- Description: M.Ing. , This thesis is about the gain equalization of erbium doped fibre amplifiers (EDFA), which is a key technology for enabling wavelength-division multiplexed (WDM) optical communication systems. In order to flatten dynamically the EDFA gain spectrum, a tuneable long-period grating filter was demonstrated. Long-period gratings were fabricated by using a KrF excimer laser combined with the metal amplitude mask technique. The transmission spectrum characteristic of the long- period grating was simulated theoretically by the coupled-mode theory. The coupling between the core and cladding modes of the long-period grating was investigated both experimentally and theoretically. The EDFA was constructed by using the forward pumping configuration consisting of pump laser source, WDM couplers, an optical isolator, and the erbium-doped fibre. The EDFA was characterized theoretically and experimentally for WDM applications. The tuneable long-period grating filter design is based on the tuneable coupler that uses the Mach-Zehnder interferometer configuration. The tuneable filter was demonstrated by equalizing the EDFA gain spectrum and the amplified spontaneous emission (ASE) source. The main advantage of this filter compared to other optical filters is its tuneability of the attenuation over a wide range of pump power.
- Full Text:
Methodologies used for increasing the output power of an Erbium doped fiber ring laser
- Authors: Le Roux, Josias Johannes
- Date: 2014-09-17
- Subjects: Optical amplifiers , Optical fibers , Lasers , Optical communications
- Type: Thesis
- Identifier: uj:12332 , http://hdl.handle.net/10210/12119
- Description: M.Ing. (Electrical And Electronic Engineering) , Please refer to full text to view abstract
- Full Text:
- Authors: Le Roux, Josias Johannes
- Date: 2014-09-17
- Subjects: Optical amplifiers , Optical fibers , Lasers , Optical communications
- Type: Thesis
- Identifier: uj:12332 , http://hdl.handle.net/10210/12119
- Description: M.Ing. (Electrical And Electronic Engineering) , Please refer to full text to view abstract
- Full Text:
Stabilised C-band dual wavelength erbium doped fibre ring laser
- Authors: Mthukwane, Clarence Modise
- Date: 2018
- Subjects: Optical fibers , Lasers - Industrial applications , Optical amplifiers , Bragg gratings , Erbium
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/280397 , uj:30130
- Description: M.Ing. (Electrical Engineering) , Abstract: In this dissertation, the realisation of a dual wavelength erbium doped fibre ring cavity laser configuration is discussed. The power stability and wavelength stability of a dual wavelength erbium doped fibre laser is investigated. The lasing wavelengths of the fibre laser are 1555.12 nm and 1560.32 nm. The laser is based on a ring cavity resonator which employs a 3 dB coupler and fibre Bragg gratings, as the wavelength selective component arrangement. The active medium in the cavity is a 3.2 m long erbium doped fibre with an absorption of 11.38 dB/m at 980 nm. To achieve simultaneous dual wavelength lasing with an erbium doped fibre laser configuration, there is one major challenge that must be overcome. The challenge is to correct the cavity losses on the selected wavelengths to achieve oscillation for all desired channels. In addition, because of the unevenness of the EDF gain profile, the threshold power for individual wavelengths is different. Subsequently, loss control across each of the selected wavelengths is required to balance the power difference between the wavelengths. The power and wavelength stability of the dual lasing wavelengths is investigated using an optical loop mirror with a 1 m length of single-mode fibre, and an unpumped erbium doped fibre of length 0.5 m, 1 m and 1.5 m. Also, the effect of changing the cavity length on the uniformity of the wavelength power increase relative to an increase in pump power together with the power and spectral stability of the lasing wavelengths is investigated. A 1m long Sagnac loop with a 70:30 coupling ratio was used to adjust the threshold power for simultaneous lasing of the two wavelengths. An increase in cavity length led to a good prospect for a stable dual wavelength laser with an output power difference of 0.4 dBm between the dual wavelengths and a power stability of 0.4 dB. The multi-wavelength and narrow spectral width of 0.19 nm and 0.20 nm of the laser can be used for dispersion measurement in wavelength division multiplexed communication links which consist of more than one wavelength. The laser was characterised for simultaneous dual wavelength output power response and power stability. The project presents the characterisation of an erbium doped fibre ring laser. The laser is cost effective and flexible in selecting preferred components for optimal performance in terms of power and wavelength stability, wavelength selectivity and narrow spectral width. Erbium doped fibre ring laser lasers are commercially available and are showing great promise in terms of their formidability and compatibility with current industrial requirements.
- Full Text:
- Authors: Mthukwane, Clarence Modise
- Date: 2018
- Subjects: Optical fibers , Lasers - Industrial applications , Optical amplifiers , Bragg gratings , Erbium
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/280397 , uj:30130
- Description: M.Ing. (Electrical Engineering) , Abstract: In this dissertation, the realisation of a dual wavelength erbium doped fibre ring cavity laser configuration is discussed. The power stability and wavelength stability of a dual wavelength erbium doped fibre laser is investigated. The lasing wavelengths of the fibre laser are 1555.12 nm and 1560.32 nm. The laser is based on a ring cavity resonator which employs a 3 dB coupler and fibre Bragg gratings, as the wavelength selective component arrangement. The active medium in the cavity is a 3.2 m long erbium doped fibre with an absorption of 11.38 dB/m at 980 nm. To achieve simultaneous dual wavelength lasing with an erbium doped fibre laser configuration, there is one major challenge that must be overcome. The challenge is to correct the cavity losses on the selected wavelengths to achieve oscillation for all desired channels. In addition, because of the unevenness of the EDF gain profile, the threshold power for individual wavelengths is different. Subsequently, loss control across each of the selected wavelengths is required to balance the power difference between the wavelengths. The power and wavelength stability of the dual lasing wavelengths is investigated using an optical loop mirror with a 1 m length of single-mode fibre, and an unpumped erbium doped fibre of length 0.5 m, 1 m and 1.5 m. Also, the effect of changing the cavity length on the uniformity of the wavelength power increase relative to an increase in pump power together with the power and spectral stability of the lasing wavelengths is investigated. A 1m long Sagnac loop with a 70:30 coupling ratio was used to adjust the threshold power for simultaneous lasing of the two wavelengths. An increase in cavity length led to a good prospect for a stable dual wavelength laser with an output power difference of 0.4 dBm between the dual wavelengths and a power stability of 0.4 dB. The multi-wavelength and narrow spectral width of 0.19 nm and 0.20 nm of the laser can be used for dispersion measurement in wavelength division multiplexed communication links which consist of more than one wavelength. The laser was characterised for simultaneous dual wavelength output power response and power stability. The project presents the characterisation of an erbium doped fibre ring laser. The laser is cost effective and flexible in selecting preferred components for optimal performance in terms of power and wavelength stability, wavelength selectivity and narrow spectral width. Erbium doped fibre ring laser lasers are commercially available and are showing great promise in terms of their formidability and compatibility with current industrial requirements.
- Full Text:
Towards an integrated optic tuneable gain equalizer for erbium-doped fibre amplifiers
- Authors: Botha, Roelene
- Date: 2009-02-26T12:16:33Z
- Subjects: Optical amplifiers , Optical fibers , Optical communications
- Type: Thesis
- Identifier: uj:8146 , http://hdl.handle.net/10210/2153
- Description: M.Ing. , Long distance optical communication systems experience a large degree of attenuation due to fibre losses, necessitating signal amplification. Erbium Doped Fibre Amplifiers (EDFAs) have found widespread use as all-fibre optical amplifiers, but exhibit unequal amplification of different wavelengths. Since the gain spectrum is signal-power and pump-power dependent, each EDFA spectrum may differ considerably, and a tuneable gain equalizer is required. A tuneable long-period grating (LPG) can be implemented as a gain equalizer for EDFAs. This dissertation deals with the design of an integrated optic version of the tuneable equalizing filter. The various components of which the device comprises, including optical couplers, Mach-Zehnder interferometers and an LPG, are investigated. The integrated optics designs of these components are then done using the BeamPROP software package. The use and optical properties of germania-doped silica as photosensitive waveguide material is studied. The production of the films for the gain equalizer, using electron-cyclotron resonance plasma-enhanced chemical vapour deposition, is discussed. Characterization of these films was carried out using spectroscopic ellipsometry and infrared spectroscopy. The optical constants, thickness, germania content and hydroxyl absorption was calculated using these measurements.
- Full Text:
- Authors: Botha, Roelene
- Date: 2009-02-26T12:16:33Z
- Subjects: Optical amplifiers , Optical fibers , Optical communications
- Type: Thesis
- Identifier: uj:8146 , http://hdl.handle.net/10210/2153
- Description: M.Ing. , Long distance optical communication systems experience a large degree of attenuation due to fibre losses, necessitating signal amplification. Erbium Doped Fibre Amplifiers (EDFAs) have found widespread use as all-fibre optical amplifiers, but exhibit unequal amplification of different wavelengths. Since the gain spectrum is signal-power and pump-power dependent, each EDFA spectrum may differ considerably, and a tuneable gain equalizer is required. A tuneable long-period grating (LPG) can be implemented as a gain equalizer for EDFAs. This dissertation deals with the design of an integrated optic version of the tuneable equalizing filter. The various components of which the device comprises, including optical couplers, Mach-Zehnder interferometers and an LPG, are investigated. The integrated optics designs of these components are then done using the BeamPROP software package. The use and optical properties of germania-doped silica as photosensitive waveguide material is studied. The production of the films for the gain equalizer, using electron-cyclotron resonance plasma-enhanced chemical vapour deposition, is discussed. Characterization of these films was carried out using spectroscopic ellipsometry and infrared spectroscopy. The optical constants, thickness, germania content and hydroxyl absorption was calculated using these measurements.
- Full Text:
- «
- ‹
- 1
- ›
- »