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"ABSTRACT As transmission medium in optical communication system, optical fiber is also characterized by elastic properties beside of transmission properties of optical fiber. The Young Modulus of Elasticity of optical fiber could be measured by considering a bare optical fiber as cantilever which resonant with an acoustical vibration. To detect the cantilever vibration, a HeNe laser light is launched into the cantilever of optical fiber through its free end and the output laser light is detected by a PMT and observed by the channel 2 of an oscilloscope. Channel 1 of the oscilloscope observes the signal of the acoustical vibration. Regulating both the frequency and amplitude of the vibration or the position of the pinhole of the PMT, the resonance frequency of the cantilever could be detected accurately. Using the data of the resonance frequencies of various length of the cantilever has been calculated. "

"In signal transmission through an optical fiber, a bending fiber causes degradation of efficiency. Due to mode conversion and radiation loss. Considering a light power radiated from a bending fiber has a possibility to be utilized as detectable signal, it is proposed an optical tap by using bending fiber.The study is devoted to design and construction of optical tap for fiber link, without any other optical element. The signal quality of the radiated light from optical fiber bending has been investigated in various angle of detection and in various radius of curvature. The result shows that the radiated signal has similar shapes of distribution of 20 degrees. And the bending loss increases if the radius of curvature decreases.A trial of sending optical signal from one end of the fiber link shows a detected radiated signal from the bending point. It is predicted that the bending fiber can be applied as optical tap, instead of a source of power loss."

"ABSTRAKIn transmission system, the information to be transmitted from one source to several addressed receivers requires a component to distribute the information. To achieve an efficient and simple distribution circuit of information, a study on the use of fiber as information signal distributor without using other optical elements has been developed as a fiber star-coupler. The optical fiber star-coupler was constructed by chemically processing the end face of fiber into a cone-shaped. The process was carried out by chemical treatment for unjacketed fibers using HF solution. The optical signal distributed to the outgoing fibers will have as higher intensity as the nearer the fiber to the optical axis. An efficient fiber star-coupler can be achieved by arranging the optimum number of receiving fibers correspond to coupling distance and numerical aperture of the optical fibers."

"Serat optik merupakan salah satu media transmisi guided yang banyak digunakan pada saat ini karena memiliki berbagai macam kelebihan, antara lain memiliki tingkat keamanan data yang tinggi, memiliki rentang hidup yang panjang dibandingkan dengan media transmisi komunikasi lainnya, dan dapat membawa informasi dalam kapasitas yang besar. Namun, sebagai salah satu media transmisi, serat optik juga mengalami rugi-rugi saat mentransmisikan informasi, terlebih dalam rugi transmisi daya. Salah satu rugi-rugi yang menjadi perhatian adalah rugi macro bend pada serat optik. Penelitian ini akan meninjau seberapa besar pengaruh lengkungan serat optik terhadap transmisi daya menggunakan Optical Light Source (OLS) dan Optical Power Meter (OPM) dengan memvariasikan lekukan pada serat optik, variasi panjang gelombang pada Optical Light Source, serta variasi jenis serat optik yang digunakan, yaitu insensitive/sensitive bend fiber. Hasil yang diperoleh menunjukkan bahwa jenis kabel G652 mencapai bending loss sebesar -43.7 dB/unit pada dua lilitan dengan radius bending 0,5 cm, sedangkan jenis kabel G657 mencapai bending loss sebesar -50 dB/unit pada tiga lilitan dengan radius bending 0,5 cm. Bending loss mencapai hasil yang signifikan pada radius bending di bawah 3 cm. Rugi-rugi lengkungan pada serat optik dipengaruhi oleh jenis kabel pada serat optik, panjang gelombang pada sumber optik, jumlah lilitan dan radius bending, dengan faktor rugi-rugi yang paling signifikan dipengaruhi oleh radius bending.

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Optical fiber is one of the guided transmission media that is widely used today because it has various advantages, including having a high level of data security, having a long life span compared to other communication transmission media, and being able to carry information in a large capacity. However, as a transmission medium, optical fiber also suffers losses when transmitting information, especially in power transmission losses. One of the losses of concern is the macro bend loss in optical fiber. This study will discuss how much influence optical fiber has on power transmission using Optical Light Source (OLS) and Optical Power Meter (OPM) by varying the optical fiber, length variations on Optical Light Source, and optical variations used, namely insensitive/sensitive bend. fiber. The results obtained indicate that the G652 cable type achieves a bending loss of -43.7 dB/unit in two turns with a bending radius of 0.5 cm, while the G657 cable type achieves a bending loss of -50 dB/unit in three turns with a bending radius of 0.5. cm. Bending loss achieves significant results at bending radii below 3 cm. Bending loss in optical fiber is influenced by the type of cable in the optical fiber, the wavelength of the optical source, the number of turns, and the bending radius, with the most significant loss factor being influenced by the bending radius."

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Dalam kurun beberapa tahun ini telah terjadi pertumbuhan eksponensial terus-menerus dalam permintaan transmisi serat optik untuk aplikasi penghubung antar pulau, sistem fiber darat melewati bibir pantai (festoon), dan penggunaan transmisi terestrial rentang panjang untuk daerah terpencil. Sistem transmisi rentang panjang tanpa repeater dengan menggunakan amplifikasi Raman terdistribusi adalah solusi hemat biaya untuk menjembatani jarak transmisi beberapa ratus kilometer. Kerr nonlinier distorsi dan Raman amplifier noise telah diidentifikasi sebagai dua faktor kendala utama dalam meningkatkan performansi transmisi dan peningkatan jarak jangkauan. Konfigurasi fiber core hibrida yang terbentuk dari struktur tiga segmen diusulkan sebagai alternatif pengganti atas fiber core konvensional berstruktur homogen satu segmen. Karena ukuran fiber core dapat berubah sepanjang propagasi, maka rumus baku amplifikasi Raman harus ditulis ulang menjadi rumus umum dimana ukuran fiber core tidak lagi merupakan nilai konstan tetapi variabel atas jarak sepanjang propagasi. Dengan menggunakan persamaan Raman standar dan penulisan ulang ukuran fiber core (fiber effective core area) sebagai fungsi jarak propagasi, maka penelitian ini mengusulkan pemodelan rumusan umum yang baru (new generalized formula) agar sesuai untuk diaplikasikan pada sistem dengan struktur multi-segmen. Hasil analisis numerik menunjukkan bahwa perbaikan atas nonlinear phase shift dan optical signal-to-noise ratio (OSNR) dapat dicapai secara bersamaan. Pencapaian ini tidak mungkin didapat jika hanya menggunakan struktur konvensional dengan fiber core tunggal (homogen). Dilakukan simulasi untuk mengetahui peningkatan kinerja transmisi dan perpanjangan jarak transmisi rentang panjang tanpa menggunakan repeater. Penggunaan fiber core hibrida dengan struktur tiga segmen mengindikasikan adanya peningkatan fleksibilitas gain profile pada sistem transmisi menggunakan Raman amplifier-terdistribusi, pengurangan dampak negatif dari efek nonlinier Kerr yang disebabkan oleh tingginya sinyal power, dan peningkatan OSNR yang disebabkan oleh penurunan amplified spontaneous emissions (ASE) dari Raman pump. Rentang transmisi tiga segmen dengan inti serat optik berstruktur hibrida dapat mengurangi akumulasi nonlinear phase shift sebesar 1.29 radian, meningkatkan OSNR sebesar 0.31 dB, dan meningkatkan performansi transmisi atas sinyal bermodulasi DQPSK dibandingkan dengan fiber core konvensional berstruktur tunggal. Hasil simulasi performansi BER pada sinyal berkecepatan 80 Gb/s menunjukkan penurunan OSNR yang dibutuhkan sebesar 2.71 dB untuk target BER sebesar 10^-9. Dilakukan pengujian atas BER performansi untuk berbagai kecepatan data (40, 60, 80, dan 100 Gb/s) dengan hasil yang menunjukkan stabilitas dan konsistensi kinerja sistem untuk berbagai kecepatan data yang berbeda. Studi analitik dan simulasi kanal-tunggal pada panjang gelombang tunggal dengan menggunakan fiber core tiga segmen berstruktur hibrida ini dapat digunakan sebagai pedoman dasar untuk studi lebih lanjut untuk skema amplifikasi broadband Raman multi-kanal multi-panjang gelombang. Selanjutnya dalam penelitian ini, berdasarkan pemodelan amplifikasi Raman terdistribusi dua arah dilakukan pengujian gain profile atas berbagai kemungkinan perbandingan power antara forward pump dan backward pump. Dilakukan peninjauan analitik atas pengaruh dari ukuran fiber core dan distorsi sinyal akibat Kerr nonlinier efek. Studi ini menunjukkan bahwa penggunaan inti serat optik berukuran besar dapat menghasilkan OSNR yang lebih tinggi dan nonlinear phase shift yang lebih kecil dibandingkan dengan yang berukuran kecil, oleh karena itu fiber core berukuran besar dapat diharapkan memberikan kinerja transmisi yang lebih baik dibandingkan dengan fiber core berukuran kecil. Dua jenis bentuk pulsa (NRZ dan RZ) dimodelkan dan disimulasikan untuk mengurangi distorsi nonlinier dan meningkatkan kinerja transmisi serat kemungkinan untuk memperpanjang jarak transmisi sistem rentang panjang. Hasil simulasi 40 Gb/s dengan modulasi DPSK berjarak 400 km menggunakan fiber 150 μm² menunjukkan bahwa target BER sebesar 10^-9 dapat dicapai oleh sinyal dengan bentuk pulsa RZ dengan OSNR pinalti sebesar 2.90 dB dibandingkan pulsa NRZ dengan OSNR pinati sebesar 4.68 dB, hal ini menunjukkan pengurangan OSNR pinalti sebesar 1.78 dB untuk pulsa RZ. Pengaturan sinyal power yang tepat pada titik trasmit sangat penting untuk mencapai penanganan noise yang lebih baik serta mendapatkan tingkat OSNR yang mencukupi pada sisi penerima. Dilakukan penyelidikan atas dampak dari fluktuasi input power terhadap performansi transmisi. Jika input power berfluktuasi dari nilai optimum (seperti 0 dBm pada simulasi ini), maka fiber dengan ukuran effective core area yang lebih besar dan menggunakan sinyal dengan pulsa RZ akan memberikan toleransi yang lebih baik atas perubahan input power dan memberikan transmisi pinalti lebih kecil, hal ini sangat cocok untuk transmisi rentang panjang.

 

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Over the years, there has been continual exponential growth in the demand for optical fiber transmission for applications in the areas of inter-island hopping, coastal festoon systems, and the use of single ultra-long span terrestrial links in remote regions. Ultra-long span unrepeatered systems using distributed Raman amplification are cost-effective solutions for bridging several hundred kilometers transmission distances. Kerr nonlinear distortion and Raman amplifier noise have been identified as two major limiting factors in improving the transmission performance and extending reachable distance. A configuration of a hybrid fiber effective core area consisting of a three-segment structure was proposed as an alternative to conventional single-segment fiber effective core area structure. Since the value of the fiber effective core area changes along the propagation distance, the standard Raman amplification formulas should be rewritten to generalized formulas where the fiber effective core area is no longer a constant value but a function of propagation distance. Based on standard Raman coupled equations and rewriting the fiber effective core area as a function of propagation distance, the new generalized formulas suitable for the multi-segment structure have been modeled and proposed in this study. The numerical analysis results show that improvements to the nonlinear phase shift and optical signal-to-noise ratio (OSNR) can be achieved simultaneously. This achievement would be impossible with the sole use of a conventional single fiber core structure. An improvement of the transmission performance and the possibility to extend the transmission distance of unrepeatered ultra-long span system were simulated. The introduction of a hybrid fiber effective core area in a three-segment structure indicated an increase in the flexibility of the gain profile of the distributed Raman amplified link, a reduction of the negative impact of the nonlinear Kerr effect due to the high signal power, and improvement of the delivered OSNR by means of the reduction of the Raman optical pump-induced amplified spontaneous emissions (ASE). The three-segment transmission span with the hybrid fiber effective core area reduced the accumulated nonlinear phase shift by 1.29 radian, increased the delivered OSNR by 0.31 dB, and improved the transmission performance of the DQPSK-modulated signal compared to the conventional single fiber core structure. The simulated BER performance of the 80 Gb/s data signal showed the reduction of the required OSNR by 2.71 dB to achieve the target BER of 10⁻⁹. BER performance for various data rates (40, 60, 80, and 100 Gb/s) was examined, and the results showed the stability and consistency of the system performance across different data rates. These single-channel analytical and simulation studies on a three-segment hybrid fiber effective core area structure could be used as basic guidelines for further studies on the multi-channel broadband multi-wavelength Raman amplification scheme. Furthermore in this study, the gain profiles of various forward and backward pump power ratios are examined based on bidirectional pumped distributed Raman amplification model. The impact of fiber effective core area to amplification gain of bidirectional Raman, signal distortion due to Kerr nonlinear effect, Raman amplifier induced noise, and optical signal-to-noise ratio are analytically investigated. This study shows that a large effective core area fiber provides higher OSNR and smaller nonlinear phase shift compare to a small one. Therefore a large effective core area fibers can be expected to provide a better transmission performance compared to a small effective core area fiber. Two types of pulse shapes (NRZ and RZ) are modeled and simulated to reduce the nonlinear distortion and improve the transmission performance and the possibility to extend the transmission distance of ultra-long span system. Simulation of  DBPSK modulated signal at a data rate of 40 Gb/s for 400 km transmission link using a large effective core fiber 150 μm² shows that the target BER of 10^-9 can be achieved by RZ pulse shaped signal with OSNR penalty at 2.90 dB compared to NRZ pulse at 4.68 dB, a significant OSNR penalty reduction of 1.78 dB on RZ pulse. An appropriate setting of the signal power level at the fiber launching point is important to achieve better noise performance to get an acceptable OSNR level at the receiver. The impact of input power fluctuation on the transmission performance and required OSNR are investigated. When the input power fluctuates from the optimum value (such as 0 dBm on our simulation), the fiber with a larger effective core area and signal in RZ pulse shape has better input power tolerance and less transmission penalty that is suitable for bidirectional Raman amplified ultra-long span systems.

 

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"This book discusses some research results for CMOS-compatible silicon-based optical devices and interconnections. With accurate simulation and experimental demonstration, it provides insights on silicon-based modulation, advanced multiplexing, polarization and efficient coupling controlling technologies, which are widely used in silicon photonics. Researchers, scientists, engineers and especially students in the field of silicon photonics can benefit from the book. This book provides valuable knowledge, useful methods and practical design that can be considered in emerging silicon-based optical interconnections and communications. And it also give some guidance to student how to organize and complete an good dissertation."

"ABSTRAKPandu gelombang optik tergandeng telah digunakan secara luas pada sistem komunikasi serat optik sebagai piranti pencabang optik seperti penggandeng arah, demultiplexer, tapis, saklar dan pembagi daya optik. Pandu gelombang tergandeng paralel dengan bentuk yang asimetris dan bentuk tirus/menyempit diketahui mempunyai sifat gandengan yang menarik dan dapat digunakan sebagai piranti pencabang apabila kondisi kerja tertentu dipenuhi. Sifat-sifat gandengan pada pandu gelombang tergandeng dianalisa secara teoritis dengan menggunakan metoda interferensi dua moda dari gelombang yang terpandu. Pemindahan daya secara total pada penggandeng arah tidak dapat terjadi kecuali kecepatan phasa atau tetapan propagasi dari kedua pandu gelombang tersebut sesuai/cocok. Simulasi sifat-sifat gandengan dilakukan dengan Metoda Propagasi Berkas Cahaya. Hasil analisa menyatakan bahwa jamak gandengan dari penggandeng arah simetris akan berkurang dengan bertambahnya panjang gelombang, dan akan berkurang dengan bertambahnya perbedaan indeks bias antara inti dan selubung. Selain itu efisiensi pemindahan days pada pandu gelombang paralel a-simetris akan menurun apabila derajat ketidaksimetrian bertambah. Sifat-sifat ini selanjutnya dapat diterapkan pada sistem pandu gelombang jamak paralel. Selanjutnya berdasarkan teknik interferensi dua moda kita dapat menganalisa karakteristik pemindahan daya dari penggandeng 3-pandu gelombang dan 5-pandu gelombang. Dalam disertasi ini diusulkan struktur baru pembagi daya 1x5 dengan struktur pandu gelombang paralel a-simetris yang mempunyai pembagian daya yang merata dan dapat dioperasikan pada daerah panjang gelombang 1.3 - 1.55 arm.Analisa sifat-sifat gandengan jugs telah dilakukan untuk struktur pandu gelombang tergandeng berbentuk tirus/menyempit. Telah dianalisa sifat gandengan dari pandu gelombang tergandeng berbentuk tirus yang simetris dan a-simetris dengan menggunakan BPM. Telah didapat hasil yang baru, yaitu bahwa penggandeng arah dengan bentuk tirus yang simetris dapat digunakan sebagai penggandeng 3-dB dengan pita panjang gelombang yang luas. Struktur ini sangat efisien sebagai pembagi daya karena ukurannya yang kecil yang disebabkan oleh jarak gandengan yang pendek dan dipertnhankannya pembagian daya yang tetap merata sepanjang arah penjalarannya. Berdasarkan hasil tersebut telah diusulkan bentuk baru pencabang-Y yang mempunyai sifat pembagian daya yang merata yang ditunjukkan oleh basil simulasi BPM. Kedua piranti tersebut telah dibuat dengan teknik Sputtering-RF pada bahan dasar SiO2. Piranti-piranti ini dapat dikembangkaa sebagai pembagi daya IxN, yang dapat digunakan pada sistem komunikasi serat optik WDM dan sistem pemroses sinyal.

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ABSTRACT

Optical coupled waveguide has been widely used in optical communication systems as a branching device such as directional couplers, de-multiplexer, filter, switching device and power divider. Parallel coupled waveguide with asymmetrical structure and tapered form are known to have interesting coupling characteristics and can be utilized as branching devices when certain working requirements are met. The coupling properties in coupled waveguides are analyzed theoretically on the basis of two modes interference effect of the propagating waves. Complete power transfer in directional coupler can not be realized, even if the phase velocity or propagation constant of the two waveguide are matched. Simulation of coupling properties is performed by using Beam Propagation Methods. As a result of the analysis, it is shown that the coupling length of symmetrical directional coupler decreases as the wavelength increases and increases as the index difference between core and cladding decreases. On the other hand, in the parallel asymmetrical structure the power coupling efficiency decreases as the asymmetry of the structure increases. These properties also can be extend applied to multi-parallel wave guide systems. Based on modes interference techniques we can analyze power transfer characteristics of 3-guides and 5-guides couplers. In this dissertation we proposed a novel 1x5 power divider based on asymmetrical parallel coupled waveguides structure which has an evenly power dividing ratio , and can be operated at the wavelength range of 1.3 - 1.55 um.

Analysis of the coupling properties has also been carried out for the tapered-form coupled waveguide structure. We have analyzed coupling characteristics of both asymmetrical and symmetrical tapered-form waveguides by using BPM. We have discovered a new result that the directional coupler with symmetrical tapered-form can be used as a 3-db coupler with a broadband characteristic. This structure is very efficient as a power divider because of its small size due to short coupling length and even power dividing ratio along the propagation direction. Based on this new result obtained from our analysis, we further proposed a novel structure of Y-branch coupler waveguide, which excellent power dividing properties are exhibited by our BPM simulation. Both devices have been fabricated by RF-sputtering technique on SiO2 based material. These devices can be developed as an lxN power splitter, which can be applied in a wide WDM optical communication systems and Signal processing systems."