Optical Beat Interference in Optical Communication System
Subcarrier Multiplexing (SCM) can be used to increase the capacity of any optical network. Both Single-Optical-Carrier (SOC) and Multiple- Optical-Carrier (MOC) SCM systems can be employed. However, in SCMMOC systems, when two lasers carrying subcarrier channels operate with very close spaced wa...
| Main Author: | |
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| Format: | Thesis |
| Language: | English English |
| Published: |
2006
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/6105/1/FK_2006_17.pdf |
| _version_ | 1825943988630192128 |
|---|---|
| author | Al-Qdah, Malik Taysir |
| author_facet | Al-Qdah, Malik Taysir |
| author_sort | Al-Qdah, Malik Taysir |
| collection | UPM |
| description | Subcarrier Multiplexing (SCM) can be used to increase the capacity of
any optical network. Both Single-Optical-Carrier (SOC) and Multiple-
Optical-Carrier (MOC) SCM systems can be employed. However, in SCMMOC
systems, when two lasers carrying subcarrier channels operate
with very close spaced wavelength, beating between the lasers and
beating between the lasers and Four-Wave Mixing (FWM) terms can
occur. This will increase the noise at the photodetector. This type of
noise is called Optical Beat Interference (OBI) and it is dependent on the
accumulated Chromatic Dispersion (CD) experienced
transmission. This thesis establishes a new approach to reduce OBI by
suppressing the optical carrier. The effect of OBI in the presence of FWM
is also examined and analyzed. Additionally, applications of OBI in
optical communications are investigated, particularly for measuring CD
and the modulator frequency chirp.The new approach for OBI reduction uses optical carrier suppression.
This method achieved a 28 dB improvement in the Carrier-To-
Interference (CIR) ratio. In addition, OBI penalty in SCM-MOC network in
the presence of FWM is studied mathematically and verified through a
simulation exercise, which shows that the maximum number of
subcarrier or the bandwidth of the SCM-MOC system will be limited by
Main-Beating and FWM-Beating when FWM is present.
The novel technique for CD measurement is performed by
simultaneously launching a pump and probe optical signals at ol
angular optical frequency separation, and two phase-conjugated terms
into the SMF. The relative power of the beat frequencies that appear
after the photodetector at 01 and at 201 is used to determine the
accumulated CD. This technique was successfully demonstrated using
a Semiconductor Optical Amplifier (SOA) as a phase conjugator to
achieve a 19 dB relative power variation as a result of up to 1900 ps/nm
CD change.
A new method to measure the modulator frequency chirp parameter
using OBI is performed in two steps. In the first step, the frequency
separation between two optical signals passing through a phase
conjugator is changed, produces a resonance reference frequency as a
result of the accumulated fiber CD. In the second step, an RF modulated signal passes through the same length of fiber as in the first step. A
second resonance frequency is produced as a result of fiber CD and
modulator chirp. The difference between the two resonance frequencies
is used to measure the modulator chirp. The new method achieves a
measurement range of * 5 and maximum resonant frequency of 8.1 GHz
at an accumulated CD 1632 ps/nm. |
| first_indexed | 2024-03-06T07:08:55Z |
| format | Thesis |
| id | upm.eprints-6105 |
| institution | Universiti Putra Malaysia |
| language | English English |
| last_indexed | 2024-03-06T07:08:55Z |
| publishDate | 2006 |
| record_format | dspace |
| spelling | upm.eprints-61052023-10-09T02:48:27Z http://psasir.upm.edu.my/id/eprint/6105/ Optical Beat Interference in Optical Communication System Al-Qdah, Malik Taysir Subcarrier Multiplexing (SCM) can be used to increase the capacity of any optical network. Both Single-Optical-Carrier (SOC) and Multiple- Optical-Carrier (MOC) SCM systems can be employed. However, in SCMMOC systems, when two lasers carrying subcarrier channels operate with very close spaced wavelength, beating between the lasers and beating between the lasers and Four-Wave Mixing (FWM) terms can occur. This will increase the noise at the photodetector. This type of noise is called Optical Beat Interference (OBI) and it is dependent on the accumulated Chromatic Dispersion (CD) experienced transmission. This thesis establishes a new approach to reduce OBI by suppressing the optical carrier. The effect of OBI in the presence of FWM is also examined and analyzed. Additionally, applications of OBI in optical communications are investigated, particularly for measuring CD and the modulator frequency chirp.The new approach for OBI reduction uses optical carrier suppression. This method achieved a 28 dB improvement in the Carrier-To- Interference (CIR) ratio. In addition, OBI penalty in SCM-MOC network in the presence of FWM is studied mathematically and verified through a simulation exercise, which shows that the maximum number of subcarrier or the bandwidth of the SCM-MOC system will be limited by Main-Beating and FWM-Beating when FWM is present. The novel technique for CD measurement is performed by simultaneously launching a pump and probe optical signals at ol angular optical frequency separation, and two phase-conjugated terms into the SMF. The relative power of the beat frequencies that appear after the photodetector at 01 and at 201 is used to determine the accumulated CD. This technique was successfully demonstrated using a Semiconductor Optical Amplifier (SOA) as a phase conjugator to achieve a 19 dB relative power variation as a result of up to 1900 ps/nm CD change. A new method to measure the modulator frequency chirp parameter using OBI is performed in two steps. In the first step, the frequency separation between two optical signals passing through a phase conjugator is changed, produces a resonance reference frequency as a result of the accumulated fiber CD. In the second step, an RF modulated signal passes through the same length of fiber as in the first step. A second resonance frequency is produced as a result of fiber CD and modulator chirp. The difference between the two resonance frequencies is used to measure the modulator chirp. The new method achieves a measurement range of * 5 and maximum resonant frequency of 8.1 GHz at an accumulated CD 1632 ps/nm. 2006-02 Thesis NonPeerReviewed text en http://psasir.upm.edu.my/id/eprint/6105/1/FK_2006_17.pdf Al-Qdah, Malik Taysir (2006) Optical Beat Interference in Optical Communication System. Doctoral thesis, Universiti Putra Malaysia. Optical communications - Case studies English |
| spellingShingle | Optical communications - Case studies Al-Qdah, Malik Taysir Optical Beat Interference in Optical Communication System |
| title | Optical Beat Interference in Optical Communication System |
| title_full | Optical Beat Interference in Optical Communication System |
| title_fullStr | Optical Beat Interference in Optical Communication System |
| title_full_unstemmed | Optical Beat Interference in Optical Communication System |
| title_short | Optical Beat Interference in Optical Communication System |
| title_sort | optical beat interference in optical communication system |
| topic | Optical communications - Case studies |
| url | http://psasir.upm.edu.my/id/eprint/6105/1/FK_2006_17.pdf |
| work_keys_str_mv | AT alqdahmaliktaysir opticalbeatinterferenceinopticalcommunicationsystem |