Univ., Diss.--Kaiserslautern.

Zugl.: Stuttgart, Universiẗat, Diss., 2002.

Zugl.: Kaiserslautern, Universiẗat, Diss., 2003.

Fiber nonlinearity can cause interactions and crosstalk between co-propagating dense wavelength division multiplexed channels in high capacity optical fiber communication systems. The crosstalk between channels leads to degradation of the bit error performance of the system. One of the mechanisms of this crosstalk is Four-Wave-Mixing (FWM) caused by the fiber nonlinearity. It is important to have an analytic model for the FWM to estimate and minimize the impact of FWM for a given transmission system design. Conventional analytic models for FWM ignore the inter-channel walk-off effect. In this thesis a model for FWM is developed which rigorously accounts for the walk-off effect. The model is derived for degenerate and non-degenerate FWM. This model is derived for conventional RZ-OOK and the emerging RZ-DPSK modulation formats. A detailed physical understanding of the walk-off contribution to the FWM noise is developed. The first direct comparison, between an analytic model for FWM and split-step Fourier (SSF) simulations for the general case of random modulated channels is presented, for a single span 10-Gb/s link. It is shown that for both RZ-OOK and RZ-DPSK modulation formats the walk-off effect significantly increases the FWM noise variance for all FWM types before any filtering at the end of fiber. When a multiplexer/de-multiplexer is used the walk-off effect is significant and observable for the degenerate FWM case but is no longer significant for the non-degenerate FWM case. In the typical situation when a sub-bit-rate electrical low pass filter is also used, the walk-off effect is effectively removed for all three types of FWM. Comparing the models for the two modulation formats it is found that the FWM noise standard deviation and related BER penalty are much smaller for RZ-DPSK as compared to that for RZ-OOK at the same average launch power.

Fiber nonlinearity can cause interactions and crosstalk between co-propagating dense wavelength division multiplexed channels in high capacity optical fiber communication systems. The crosstalk between channels leads to degradation of the bit error performance of the system. One of the mechanisms of this crosstalk is Four-Wave-Mixing (FWM) caused by the fiber nonlinearity. It is important to have an analytic model for the FWM to estimate and minimize the impact of FWM for a given transmission system design. Conventional analytic models for FWM ignore the inter-channel walk-off effect. In this thesis a model for FWM is developed which rigorously accounts for the walk-off effect. The model is derived for degenerate and non-degenerate FWM. This model is derived for conventional RZ-OOK and the emerging RZ-DPSK modulation formats. A detailed physical understanding of the walk-off contribution to the FWM noise is developed. The first direct comparison, between an analytic model for FWM and split-step Fourier (SSF) simulations for the general case of random modulated channels is presented, for a single span 10-Gb/s link. It is shown that for both RZ-OOK and RZ-DPSK modulation formats the walk-off effect significantly increases the FWM noise variance for all FWM types before any filtering at the end of fiber. When a multiplexer/de-multiplexer is used the walk-off effect is significant and observable for the degenerate FWM case but is no longer significant for the non-degenerate FWM case. In the typical situation when a sub-bit-rate electrical low pass filter is also used, the walk-off effect is effectively removed for all three types of FWM. Comparing the models for the two modulation formats it is found that the FWM noise standard deviation and related BER penalty are much smaller for RZ-DPSK as compared to that for RZ-OOK at the same average launch power.

¡@¡@The ever-increasing requirement for more bandwidth to the office, home, and mobile devices is driving the deployment of high-speed optical communication systems. Differential quadrature phase-shift keying (DQPSK) is one of the most attractive and advanced modulation format in recent years, and this format increases the capacity and efficiency in optical fiber communication systems. ¡@¡@DQPSK is able to transmit two bits per symbol. That is to say that DQPSK has twice spectral efficiency compared to DPSK. In addition, DQPSK has excellent tolerance against chromatic dispersion (CD), polarization-mode dispersion (PMD), optical add-drop multiplexing (OADM) filtering, and optical noise. It makes DQPSK play an important role for next-generation optical transmission systems. ¡@¡@The wavelength-division multiplexing system (WDM) multiplexes multiple optical carriers in the single optical fiber by using the different wavelengths of laser to carry the signal. This master thesis focuses on the study of DQPSK performance in the long-haul transmission with the WDM system. ¡@¡@In the process of experiment, a special technique for DQPSK to be set up is required. When a delay demodulator is applied for the DQPSK signal, decoding is required to make the received serial data become the same as the transmitted serial sequence. As the electronic encoder or decoder is hard to realize, a program is prepared for the experiment to calculate the pre-decoded pattern sequence. Then, calculated patterns are imported to the error detector (ED) to measure the bit error rate (BER). Finally, different channels (wavelengths) of WDM transmission were observed.

The growing demand in the telecommunication systems makes the high speed transmission technology important. The Differential Quadrature Phase Shift Keying (DQPSK) is one of the most attractive and advanced modulation formats in recent years, Compared to the Differential Phase Shift Keying (DPSK), it can double the spectrum efficiency, because it can carry two bits in one symbol. In addition, the DQPSK has excellent tolerance against the chromatic dispersion (CD), the polarization mode dispersion (PMD), the optical filtering due to the optical add and drop multiplexer (OADM) and the optical noise. Compared to other coherent modulation formats, the DQPSK signal can be detected directly through a delay interferometer, and it does not need the local oscillator light, so it reduces the complexity of the system setup. We can say that the DQPSK plays an important role for the next generation system. Wavelength Division Multiplexing system (WDM) multiplexes multiple optical carriers in a single optical fiber by using different wavelength of lasers to carry the signal, therefore, increase the wavelength channels makes the system capacity increase. This master thesis focuses on the performance of the WDM system with the DQPSK modulation format in the long haul transmission system. Experiments to demonstrate the QPSK transmission are discussed. To realize the differential modulation, encoders or decoders are necessary. However, electrical encoder or decoder is hard to realize, so, a program is prepared for the experiment to calculate pre-encoded pattern or pre-decoded sequence in advance. Then, the calculated pattern is loaded in the error detector to measure the bit error rate.

Differential quadrature phase-shift keying (DQPSK) is one of the most attractive advanced modulation format in these years, because it has a good spectral efficiency. The DQPSK can transmit two bits per symbol, and it has twice the spectral efficiency of the differential phase-shift keying (DPSK). This master thesis focuses on to study the DQPSK performance in the long-haul transmission with the wavelength-division multiplexing system (WDM). The WDM multiplexes multiple optical carriers in the single optical fiber using the different wavelength lasers to carry the signal. For the experiment, the DQPSK needs a little special technique to conduct. When a delay demodulator is used for the DQPSK signal, an encoder or decoder is required to make the received serial data to be the same as the transmitted serial sequence. As an electrical encoder or decoder is difficult to realize, a software to calculate encoded pattern or decoded sequence is prepared for the experiment. Then, calculated pattern is installed into the error detector, and it is used to measure the bit error rate. Finally, the performance of the different channels of the WDM DQPSK transmission is measured experimentally. The transmission distance is 495km for the straight line experimental setup.

The primary target of this paper is to fabricate bidirectional transceiver modules based on Si-bench technology. The bidirectional transceiver modules were formed by hybrid integration of single mode lens fibers and ultra-thin thin-film filters (TFF) on silicon bench as using V-groove and U-groove techniques. The output light at 1.31 £gm was launched into the input lens fiber of the module. After passing through the TFF, the light was received by the output lens fiber of the module. The insertion loss of the module at the 1.31 £gm light was -0.68 dB. On the other hand, incoming lights at 1.49£gm and 1.55£gm were received from the output lens fiber. Lights at 1.49£gm will pass through the filter, and was received by the output lens fiber of the module. The insertion loss of the module at the 1.49 £gm light was -0.65 dB. The 1.55£gm wavelength lights received from the lens fiber are reflected by the filter and collected by the multimode fiber to the photo diode. The insertion loss of the module at the 1.55 £gm light was -0.58 dB.

No description available.