Design And Development Of Simplex-To-Full Duplex Converter (Sfdc)

Existing fiber optic network employ simplex transmission scheme where two fibers are needed, each to transmit and received signals between connecting points. The increasing demand has seen fiber, particularly in the metro area, are used up in no time. The conventional solution is to install new fibers to support new customers. However fiber installation are always expensive and fussy. Thus, a new approach is desirable in solving the problem. In this thesis, new technique is proposed to double the link bandwidth by fully utilizing the two fiber cores. The technique is based on the basic ligthwave principle that two photons do not know each other. Therefore the optical signals, transmitted and received ones can be made to propagate in the opposite direction in the same fiber, as long as they can be split and isolated at the receiver side. The techniques proposed here in achieving the goal is simple but quite powerful. The components used in developing the device are all passive products. Each of them was characterized prior to developing them according to the design. Then the whole device was tested further both on its own, and in network environment.From the tests conducted, it is important to reduce the reflection from transmitters to adjacent receivers, which is due to SFDC directivity. From the study it is found that the minimum isolation needed between actual and reflected signal to achieve good transmission quality is around 13 dB. Testing on SDH network was successfully conducted on over 50 km fiber link with zero errors. The test was conducted in both laboratory and testbed environment, with cooperation from Telekom Malaysia. Testing on WDM system was conducted in laboratory environment only. The test shows that no error is introduced. Finally it is concluded that SFDC is reliable to be used as a device to realize full duplex transmission, as its realization would result in huge increase in fiber bandwidth utilization with minimum installation and maintainance complexity and cost

Effect of optical filtering on the performance of 40 Gbps DCDM systems

The effect of optical filtering on 40 Gbps on-off keying over 2 x 20, 3 x 13.33, 4 x 10, and 7 x 5.714 Gbps duty-cycle division multiplexing (DCDM) is investigated. The system can tolerate down to 30 GHz optical filter bandwidth for 2 users, and 47.5 GHz for 7 users. At this bandwidth, 40 Gbps was successfully transmitted over 464 km and 193 km SSMF using 2 and 7 users, respectively

Chromatic dispersion compensation in 40 Gbaud optical fiber WDM phase-shift-keyed communication systems

von Ahmad Fauzi AbasPaderborn, Univ., Diss., 200

Linewidth characteristics of un-cooled fiber grating Fabry–Perot laser controlled by the external optical feedback

The effect of external optical feedback (OFB) on the linewidth characteristics of un-cooled laser module is theoretically investigated. This laser that consists of a Fabry–Perot (FP) laser diode and fiber Bragg grating (FBG) realizes stable operation and relatively low-cost solution. The effects of external OFB and temperature on linewidth are calculated according to their effect on threshold carrier density (Nth). The temperature dependence (TD) of linewidth characteristics is calculated according to TD of laser parameters instead of well-known Parkovin relationship. Results show that, linewidth decreases as the external OFB reflectivity (Rext) increases. A narrow linewidth which is less than 3 kHz is obtained for Rext ≥ 0.5. In addition, the linewidth is not largely affected by temperature as compared to the DFB lasers. Also, we found that the linewidth temperature coefficient is 0.04 kHz/°C, which is small enough in comparison to 18.5 kHz/°C for the DFB laser

OCDMA multi service with zero cross correlation code in free space optics

In this paper a variable weight code for Optical Code Division Multiple Access (OCDMA) is proposed to provide differentiated services in optical network. We call it multi service zero cross correlation (MS-ZCC) where it has zero-cross correlation. Using simulation, the performance of this code is compared with the conventional variable weight (VW)-ZCC code in free space optic (FSO) environment. The newly proposed code MS-ZCC shows an improvement of 300 meters link distance for weight 2 and 8, compared to VW-ZCC

Effect of Erbium doped fiber location on double spacing multi-wavelength Brillouin-Erbium fiber laser performance

Two different locations of Erbium Doped Fiber (EDF) in dual ring configuration to generate double frequency shifted of multiwavelength Brillouin Erbium fiber laser (BEFL) have been investigated. The experimental results show that the location of EDF has important roles to determine the number of output Stoke signals and tuning range. Beside the Erbium gain, the Brillouin gain also contributes to the performance of BEFL. By putting the EDFA next to the BP, more Stokes lines with wider tuning range were obtained compare by putting the EDF next to the gain medium was observed

Ultrafast two-bit all-optical analog-to-digital conversion based on femtosecond soliton sequence sampling.

Realization of two-bit all-optical analog-to-digital conversion for an analog signal sampled by a femtosecond soliton sequence is investigated. Two approaches are suggested. The first one is based on filtering the broadened soliton spectrum after evolution over half of the soliton period in a standard single-mode fiber. In the second approach, the pulse is temporally sampled at the specified times after propagating through one soliton period. The sampled soliton sequence must be amplified to achieve an initial peak power of between 0 and 75 kW for the first method and between 0 and 66 kW for the second method. The soliton pulse-width is 50 fs. Based on the resulted peak power, the "0" or "1" bit is generated with reference to the threshold values. Subsequently, the digital gray code is produced at the outputs. The effect of inaccuracy in filter frequency and fiber length are also studied in this paper. The first method is sensitive to variations in the filter frequency, whereas the second method is affected by the fiber length inaccuracy

Duty-cycle division multiplexing (DCDM): a novel and economical optical multiplexing and electrical demultiplexing technique for high speed fiber optics networks

A new multiplexing and demultiplexing technique based on duty cycle division is proposed, thus the name duty cycle division multiplexing (DCDM). DCDM can be applied in both electrical and optical domains. The new technique allows for more efficient use of time slots as well as the spectrum, taking advantage of both the conventional TDM and FDM. In this paper, three channels operating at the same speed of 10 Gbps are multiplexed in the optical domain and demultiplexed in the electrical domain. The performance comparison is made against 30 Gbps TDM, and the experimental simulation results show that the minimum sensitivity achieved is -26 dBm and -25.5 dBm for the two systems respectively, thus a 0.5 dB improvement

A ground based circular synthetic aperture radar

Detecting on-the-ground objects is a subject of interest for some applications. Typical example is foreign object detection on the airport runway. In response to this demand, a ground-based Circular Synthetic Aperture Radar (CSAR) system is proposed and explained in the paper. In the proposed CSAR, the antennas represent a circular movement trajectory. Wideband Linear Frequency (LFM) chirps were used for transmission. A simulation model for CSAR, based on the Doppler Effect between the radar and object is developed in this paper. In addition, a processing method for object detection using correlation between image data produced by simulation and experimental data is developed. The resultant of the simulated model at each point, which represents the object's behavior in an ideal and clutter-free environment, is used as a template for object detection. Simulation and experimental results demonstrate that the proposed method is well suited in detecting small objects at different positions