Reduction of interchannel interference noise in a two-channel grating-based OCDMA system using a nonlinear optical loop mirror
Abstract: Abstract-We show that a nonlinear optical switch can be used to suppress the interchannel noise generated under multiuser operation within a coherent, direct-sequence optical code-division multiple-access (OCDMA) system. By incorporating a simple nonlinear optical loop mirror (NOLM) within the receiver, we demonstrate a 3.6-dB power penalty reduction in a two-channel 1.25-Gb/s 64-chip 160-Gchip/s grating-based direct-sequence OCDMA system. Even greater improvements in system performance were obtained at a data… Show more
Search citation statements
Paper Sections
Citation Types
Year Published
Publication Types
Relationship
Authors
Journals
Cited by 23 publications
References 6 publications
Recent developments in optical communication systems have increased the performance of optical networks. Low attenuation fiber optics, high spectral purity lasers and optical amplifiers, among others, are systems that have allowed to transport terabits per second across thousands of kilometers, in a more reliable, secure and efficient manner, compared to radiofrequency (RF) systems. New optical access network technologies such as EPON and GPON are also providing Gbit/s connectivity to customers in both the enterprise and consumer markets. This transport capacity provides enough data for the growing demand of new communication services. The main goal of the researchers in optical networks is to provide higher-speed data transmission by exploiting the intrinsically fast behavior of the optical domain. Optical signal processing is a key technology for constructing flexible and ultra high-speed photonic networks. In this context, it will be possible to build ultra-high speed, simple and reliable optical networks, at low operational expenses, regardless of the format of the information. Before these technologies enter into commercial operation, some obstacles should be removed, such as the problem of obtaining extremely precise synchronization of the network without any optical-electrical conversion. Also, a synchronization-related problem appear at the receiver for some systems such as OTDM and OCDMA, where even the fastest photo-detectors are not able to separate the data of the desired user from the signals of the adjacent users. This means that detection of ultrashort pulses in the presence of the multiple access interference (MAI) is key in these systems. Therefore, it is vital to apply an all-optical signal processing on the received optical signal before the photo-detection. In most of the ultra-high-speed light-wave communication systems, it is an effective technique to use an optical time gating at the receiver side in order to extract the desired user's signal from the received signal. This approach requires an optical clock recovery procedure. But by increasing the data rate in optical networks the accuracy of the optical clock recovery decreases because of increasing jitter and MAI and consequently the system performance is degraded. Currently the only approach is to use a clock signal that has the same pulse-width as the data, and when the jitter is large, this technique fails to properly capture the main part of the data signal and collects more interference instead, so these techniques have to lower the data-rate to avoid large BERs. Our contributions can achieve larger signal to noise ratio versus the fixed pulse-width clock. The main goal of this work is to discuss the characteristics of the current transmission technologies, including OTDM and OCDMA, providing a detailed analytical model and proposing a solution for improving the performance of optical receivers. We use a nonlinear media (Four Wave Mixing) as a combiner in the receivers. We have modeled analytically the relationship between the input and the output of the nonlinear media systems in these techniques using nonlinear Schr枚dinger equations. Then, we solved these equations by Volterra series. Our aim is to develop analytical models of the response of the optical receiver, and validate them with simulations. Also we consider the effect of variation of the bandwidth of the clock in the performance of receivers with presence of jitter. We obtain the optimum value of the clock's bandwidth and confirm that theory and simulation results coincide. Using our proposed technique, the data-rate of the optical systems can be increased and we can achieve a lower BER for the same jitter. The goal of these efforts is the improvement of the overall performance of the network, in terms of transmission speed, bit error rate (BER), reliability and cost. The results could be applied to next-generation optical networks, in both the backbone and access scenarios. Los sistemas de comunicaciones 贸pticas aumentan constantemente su rendimiento. La disponibilidad de fibras con muy baja atenuaci贸n, l谩seres de alta pureza espectral y amplificadores 贸pticos, entre otros, hacen factible el transporte de Tbit/s a miles de kil贸metros, de una manera m谩s fiable, segura y eficiente que los sistemas basados en radiofrecuencia. Una nueva generaci贸n de redes 贸pticas de acceso, tales como EPON y GPON, ya est谩n proporcionando conectividad a Gbit/s en los mercados tanto empresarial y de consumo, lo que permitir谩 sostener la creciente demanda de los usuarios. El principal objetivo de los investigadores en el campo de las redes 贸pticas es aumentar la velocidad de transmisi贸n de datos, explotando el comportamiento intr铆nsecamente r谩pido del dominio 贸ptico. En este contexto, el procesado de la se帽al en el dominio 贸ptico es una tecnolog铆a clave para la construcci贸n de redes fot贸nicas manteniendo su simplicidad y el bajo coste de operaci贸n, as铆 como la independencia del formato de la informaci贸n. Para conseguirlo, hay obst谩culos a superar, como el problema del mantenimiento de la sincron铆a extremadamente precisa que es necesaria en redes sin conversi贸n electro-贸ptica. Otro problema es la recuperaci贸n de la sincron铆a en los detectores de los receptores usados en las t茅cnicas OTDM y OCDMA, donde incluso los fotodetectores m谩s r谩pidos no son capaces de separar los datos del usuario deseado de las se帽ales de los usuarios adyacentes. La detecci贸n de pulsos ultracortos en presencia de la interferencia debida al acceso m煤ltiple (MAI) es un reto importante. Por ello es vital aplicar procesado 贸ptico en la se帽al recibida, antes de la fotodetecci贸n. Una t茅cnica efectiva para realizar la detecci贸n es el uso de una puerta 贸ptica en el receptor, con el fin de extraer la se帽al del usuario deseado. Esto requiere recuperar por procedimientos puramente 贸pticos la se帽al de reloj. Pero al aumentar la velocidad de transmisi贸n, la precisi贸n de la recuperaci贸n de reloj disminuye debido al aumento de la fluctuaci贸n de fase (jitter) y la MAI, y en consecuencia el rendimiento del sistema se degrada. Actualmente, el enfoque usado es usar un reloj con el mismo ancho de pulso que la se帽al de datos 煤tiles, pero cuando la fluctuaci贸n de fase es grande, esta t茅cnica falla al no capturar correctamente la parte principal de la se帽al de datos y recoger una mayor interferencia. Forzando estas t茅cnicas a trabajar a velocidades inferiores a las potenciales para evitar que la tasa de errores (BER) se dispare. Este trabajo logra una mayor relaci贸n se帽al a ruido (y por tanto, una BER inferior) respecto el caso de las se帽ales con duraci贸n fija del pulso de reloj. Se han analizado las caracter铆sticas de las tecnolog铆as OTDM y OCDMA, proponiendo un modelo anal铆tico detallado, y se ha aportado una soluci贸n para mejorar el rendimiento de los receptores 贸pticos, utilizando un medio no lineal (Four Wave Mixing) como combinador en los receptores. Se ha modelado anal铆ticamente la relaci贸n entre la entrada y la salida en un medio no lineal, mediante t茅cnicas que utilizan las ecuaciones de Schr枚dinger, solucionadas mediante series de Volterra. Los modelos analiticos de la respuesta del receptor 贸ptico se han validado con simulaciones, teniendo en cuenta el efecto de la variaci贸n del ancho de banda del reloj en el rendimiento de los receptores, con presencia de fluctuaci贸n de fase. Se ha obtenido el valor 贸ptimo del ancho de banda de la se帽al de reloj, y se ha comprobado que los resultados de la teor铆a y la simulaci贸n coinciden. Los resultados obtenidos permiten incrementar la velocidad de transmisi贸n de datos en redes 贸pticas manteniendo la BER, o bien obtener una BER m谩s baja para el mismo nivel de jitter
Recent developments in optical communication systems have increased the performance of optical networks. Low attenuation fiber optics, high spectral purity lasers and optical amplifiers, among others, are systems that have allowed to transport terabits per second across thousands of kilometers, in a more reliable, secure and efficient manner, compared to radiofrequency (RF) systems. New optical access network technologies such as EPON and GPON are also providing Gbit/s connectivity to customers in both the enterprise and consumer markets. This transport capacity provides enough data for the growing demand of new communication services. The main goal of the researchers in optical networks is to provide higher-speed data transmission by exploiting the intrinsically fast behavior of the optical domain. Optical signal processing is a key technology for constructing flexible and ultra high-speed photonic networks. In this context, it will be possible to build ultra-high speed, simple and reliable optical networks, at low operational expenses, regardless of the format of the information. Before these technologies enter into commercial operation, some obstacles should be removed, such as the problem of obtaining extremely precise synchronization of the network without any optical-electrical conversion. Also, a synchronization-related problem appear at the receiver for some systems such as OTDM and OCDMA, where even the fastest photo-detectors are not able to separate the data of the desired user from the signals of the adjacent users. This means that detection of ultrashort pulses in the presence of the multiple access interference (MAI) is key in these systems. Therefore, it is vital to apply an all-optical signal processing on the received optical signal before the photo-detection. In most of the ultra-high-speed light-wave communication systems, it is an effective technique to use an optical time gating at the receiver side in order to extract the desired user's signal from the received signal. This approach requires an optical clock recovery procedure. But by increasing the data rate in optical networks the accuracy of the optical clock recovery decreases because of increasing jitter and MAI and consequently the system performance is degraded. Currently the only approach is to use a clock signal that has the same pulse-width as the data, and when the jitter is large, this technique fails to properly capture the main part of the data signal and collects more interference instead, so these techniques have to lower the data-rate to avoid large BERs. Our contributions can achieve larger signal to noise ratio versus the fixed pulse-width clock. The main goal of this work is to discuss the characteristics of the current transmission technologies, including OTDM and OCDMA, providing a detailed analytical model and proposing a solution for improving the performance of optical receivers. We use a nonlinear media (Four Wave Mixing) as a combiner in the receivers. We have modeled analytically the relationship between the input and the output of the nonlinear media systems in these techniques using nonlinear Schr枚dinger equations. Then, we solved these equations by Volterra series. Our aim is to develop analytical models of the response of the optical receiver, and validate them with simulations. Also we consider the effect of variation of the bandwidth of the clock in the performance of receivers with presence of jitter. We obtain the optimum value of the clock's bandwidth and confirm that theory and simulation results coincide. Using our proposed technique, the data-rate of the optical systems can be increased and we can achieve a lower BER for the same jitter. The goal of these efforts is the improvement of the overall performance of the network, in terms of transmission speed, bit error rate (BER), reliability and cost. The results could be applied to next-generation optical networks, in both the backbone and access scenarios. Los sistemas de comunicaciones 贸pticas aumentan constantemente su rendimiento. La disponibilidad de fibras con muy baja atenuaci贸n, l谩seres de alta pureza espectral y amplificadores 贸pticos, entre otros, hacen factible el transporte de Tbit/s a miles de kil贸metros, de una manera m谩s fiable, segura y eficiente que los sistemas basados en radiofrecuencia. Una nueva generaci贸n de redes 贸pticas de acceso, tales como EPON y GPON, ya est谩n proporcionando conectividad a Gbit/s en los mercados tanto empresarial y de consumo, lo que permitir谩 sostener la creciente demanda de los usuarios. El principal objetivo de los investigadores en el campo de las redes 贸pticas es aumentar la velocidad de transmisi贸n de datos, explotando el comportamiento intr铆nsecamente r谩pido del dominio 贸ptico. En este contexto, el procesado de la se帽al en el dominio 贸ptico es una tecnolog铆a clave para la construcci贸n de redes fot贸nicas manteniendo su simplicidad y el bajo coste de operaci贸n, as铆 como la independencia del formato de la informaci贸n. Para conseguirlo, hay obst谩culos a superar, como el problema del mantenimiento de la sincron铆a extremadamente precisa que es necesaria en redes sin conversi贸n electro-贸ptica. Otro problema es la recuperaci贸n de la sincron铆a en los detectores de los receptores usados en las t茅cnicas OTDM y OCDMA, donde incluso los fotodetectores m谩s r谩pidos no son capaces de separar los datos del usuario deseado de las se帽ales de los usuarios adyacentes. La detecci贸n de pulsos ultracortos en presencia de la interferencia debida al acceso m煤ltiple (MAI) es un reto importante. Por ello es vital aplicar procesado 贸ptico en la se帽al recibida, antes de la fotodetecci贸n. Una t茅cnica efectiva para realizar la detecci贸n es el uso de una puerta 贸ptica en el receptor, con el fin de extraer la se帽al del usuario deseado. Esto requiere recuperar por procedimientos puramente 贸pticos la se帽al de reloj. Pero al aumentar la velocidad de transmisi贸n, la precisi贸n de la recuperaci贸n de reloj disminuye debido al aumento de la fluctuaci贸n de fase (jitter) y la MAI, y en consecuencia el rendimiento del sistema se degrada. Actualmente, el enfoque usado es usar un reloj con el mismo ancho de pulso que la se帽al de datos 煤tiles, pero cuando la fluctuaci贸n de fase es grande, esta t茅cnica falla al no capturar correctamente la parte principal de la se帽al de datos y recoger una mayor interferencia. Forzando estas t茅cnicas a trabajar a velocidades inferiores a las potenciales para evitar que la tasa de errores (BER) se dispare. Este trabajo logra una mayor relaci贸n se帽al a ruido (y por tanto, una BER inferior) respecto el caso de las se帽ales con duraci贸n fija del pulso de reloj. Se han analizado las caracter铆sticas de las tecnolog铆as OTDM y OCDMA, proponiendo un modelo anal铆tico detallado, y se ha aportado una soluci贸n para mejorar el rendimiento de los receptores 贸pticos, utilizando un medio no lineal (Four Wave Mixing) como combinador en los receptores. Se ha modelado anal铆ticamente la relaci贸n entre la entrada y la salida en un medio no lineal, mediante t茅cnicas que utilizan las ecuaciones de Schr枚dinger, solucionadas mediante series de Volterra. Los modelos analiticos de la respuesta del receptor 贸ptico se han validado con simulaciones, teniendo en cuenta el efecto de la variaci贸n del ancho de banda del reloj en el rendimiento de los receptores, con presencia de fluctuaci贸n de fase. Se ha obtenido el valor 贸ptimo del ancho de banda de la se帽al de reloj, y se ha comprobado que los resultados de la teor铆a y la simulaci贸n coinciden. Los resultados obtenidos permiten incrementar la velocidad de transmisi贸n de datos en redes 贸pticas manteniendo la BER, o bien obtener una BER m谩s baja para el mismo nivel de jitter
A comparative study of the performance of seven- and 63-chip optical code-division multiple-access encoders and decoders based on superstructured fiber Bragg gratings
Abstract-We report a range of elementary optical coding and decoding experiments employing superstructured fiber Bragg grating (SSFBG) components. First, we perform a comparative study of the relative merits of bipolar and unipolar coding : decoding schemes and show that the SSFBG approach allows high-quality unipolar and bipolar coding. A performance close to that theoretically predicted for seven-chip, 160-Gchip/s -sequence codes is obtained. Second, we report the fabrication and performance of 63-chip, 160-Gchip/s, bipolar Gold sequence grating pairs. These codes are at least eight times longer than those generated by any other scheme based on fiber grating technology so far reported. Last, we describe a range of transmission system experiments for both the seven-and 63-bit bipolar grating pairs. Error-free performance is obtained over transmission distances of 25 km of standard fiber. In addition, we have demonstrated error-free performance under multiuser operation (two simultaneous users). Our results highlight the precision and flexibility of our particular grating writing process and show that SSFBG technology represents a promising technology not just for optical code division multiple access (OCDMA) but also for an extended range of other pulse-shaping optical processing applications.Index Terms-All-optical process, code division multiple access (CDMA), communication systems, fiber Bragg gratings (FBGs), multiple-access communications, optical networks, optical signal processing.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations鈥揷itations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
Contact Info
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Product
Resources
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright 漏 2024 scite LLC. All rights reserved.
Made with 馃挋 for researchers
Part of the Research Solutions Family.
