Ultrahigh-speed optical signal processing

All-optical wavelength conversion (AOWC) is one of the key functions for optical signal processing. In particular, ultrahigh-speed operation of AOWC using a nonlinear device with the abilities of integration and low-switching operation is a very important area that needs development. Moreover, four-wave mixing (FWM) has a simple scheme, which consists of a nonlinear device and an optical filter. A number of experimental demonstrations of FWM-based AOWCs that use semiconductor optical amplifiers (SOAs) or silicon waveguides have been reported.

In one of our works, we demonstrated, for the first time, error-free 320-Gbit/s FWM-based AOWC in a QD-SOA. This achievement was mainly due to the allowable carrier dynamics for the ultrahigh-speed operation and due to the sufficient FWM conversion efficiency based on the superior gain characteristics to common SOAs in the large detuning range between the pump and input data wavelengths. As a result, error-free operation with an average low power penalty of 3.4 dB was successfully achieved.






Related publications

• M. Matsuura and N. Kishi, "High-speed wavelength conversion of RZ-DPSK signal using FWM in a quantum-dot SOA," IEEE Photonics Technology Letters, vol, 23, no, 10, pp. 615-617, May 2011.
• M. Matsuura, O. Raz, F. Gomez-Agis, N. Calabretta, and H. J. S. Dorren, "320-Gbit/s wavelength conversion using four-wave mixing in quantum-dot semiconductor optical amplifiers," OSA Optics Letters, vol. 36, no. 15, pp. 2910-2912, Aug. 2011.
• M. Matsuura, O. Raz, F. Gomez-Agis, N. Calabretta, and H. J. S. Dorren, "Ultrahigh-speed and widely tunable wavelength conversion based on cross-gain modulation in a quantum-dot semiconductor optical amplifier," OSA Optics Express, vol. 19, no. 26, B551-B559, Dec. 2011.

Advanced optical signal processing

In conventional optical signal processing, an optical clock is individually generated by an optical pulse source synchronized electrically with the input data signal, and used for the seed clock. Besides, the scheme is for laboratory experiment and not practical because the converters are commonly installed in network nodes in real deployment.

This work presents a self-generating optical clock for in-line optical signal processing subsystems. To show the feasibility of this method, we demonstrate the all-optical format conversion from return-to- zero OOK (RZ-OOK) to RZ-DPSK using the self-generating optical clock and evaluate the format conversion performances.






Related publications

• H. N. Tan, M. Matsuura, and N. Kishi, "Parallel WDM signal processing in mixed NRZ and RZ transmission networks using a single optical gate with multiple switching windows," IEEE Journal of Selected Topics in Quantum Electronics, vol. 18, no. 2, pp. 926-934, Mar./Apr. 2012.
• M. Matsuura and N. Oka, "Performance of all-optical format conversion using a self-generating optical clock," IEEE Photonics Technology Letters, vol. 26. no. 22, pp. 2217-2230, Nov. 2014.

Optical networks

Multicarrier light source (MCLSs) that are able to simultaneously generate multiple carrier wavelength signals are attractive devices for optical communications. Since MCLSs easily allow control of carrier wavelengths with high wavelength grid accuracy, the MCLSs simplify carrier wavelength management in wavelength-division-multiplexing (WDM) networks. So far, a number of multicarrier distributed WDM networks using a singleMCLS have been reported. However, in such networks, a carrier wavelength dropped from the multicarrier signals for data modulation and transmission cannot be utilized by the other access node in the network again. Thus, distributed multicarrier signals are used neither effectively nor flexibly, in contrast with conventional optical add/drop multiplexing (OADM) networks that use a number of laser diodes (LDs) in each access node.

This work presents optical carrier regeneration for wavelength reuse in a multicarrier distributed OADM network. The optical carrier regeneration means that an optical return-to-zero (RZ) clock signal synchronized and wavelength-matched with an injected RZ data signal is generated from the data signal. Thus, an optical carrier for wavelength reuse can be easily regenerated from a reused RZ data signal in the network. We show that the regenerated signal has a high signal quality regardless of the quality of the reused data signal.






Related publications

• M. Matsuura and E. Oki, "Optical carrier regeneration for carrier wavelength reuse in a multicarrier distributed WDM network," IEEE Photonics Technology Letters, vol. 22, no. 11, pp. 808-810, June 2010.
• M. Keri, E. Oki, and M. Matsuura, "Wavelength assignment in multi-carrier distributed optical ring networks with wavelength reuse," IEEE/OSA Journal of Optical Communications and Networking, vol. 3, no. 4, pp. 281-289, Apr. 2011.
• M. Matsuura and E. Oki, "Scalability analysis and demonstration of distributed multicarrier reusable network with optical add/drop multiplexers," IEEE International Conference on Communications (ICC 2013), ONS-02-1, Budapest, Hungary, June 2013.

Optically powered radio-over-fiber systems

In radio-over-fiber (RoF) systems, optical fibers transmit RF signals between central station (CS) and base station (BS). This system makes it possible to transmit the RF signals with much lower loss and broader bandwidth than the coaxial cable, and is very useful for future high-speed wireless transmission systems. To simplify the BS and realize robust transmission system against disaster, we are studying optically powered RoF systems using various kinds of techniques.






Related publications

• M. Matsuura and J. Sato, "Bidirection radio-over-fiber systems using double-clad fibers for optically powered remote antenna units," IEEE Photonics Journal, vol. 7, no. 1, 7900609, Feb. 2105.
• J. Sato, H. Furugori, and M. Matsuura, "40-Watt power-over-fiber using a double-clad fiber for optically powered radio-over-fuber systems," The Optical Fiber Communication Conference and Exposition (OFC 2015), W3F.6, Los Angeles, USA, March 2015.

Plastic optical fibers for radio-over-fiber systems

In recent years, there has been greater demand for broadband optical access networks, encouraging massive utilization of large-core optical fibers such as graded-index silica multimode fibers (MMFs) and plastic optical fibers (POFs). In radio over fiber (RoF) systems using these optical fibers, modal and reflection noise appears as unwanted amplitude modulation in the received signal, and results in degradation of the RoF transmission performance.

In this work, we have evaluated the modal and reflection noise induced in MMFs and POFs. In the below work, our results show that POFs have an inherently higher tolerance to misaligned connection and less modal noise than MMFs in terms of both the error-vector magnitude (EVM) and the speckle pattern of the transmitted signals.






Related publications

• M. Matsuura, R. Furukawa, Y. Matsumoto, A. Inoue, and Y. Koike, "Evaluation of modal noise in graded-index silica and plastic optical fiber links for radio over multimode fiber systems," OSA Optics Express, vol. 22, no. 6, pp. 6562-6568, Mar. 2014.
• A. Inoue, R. Furukawa, M. Matsuura, and Y. Koike, "Reflection noise reduction effect of graded-index plastic optical fiber in multimode fiber link," OSA Optics Letters, vol. 30, no. 12, pp. 3662-3665, June 2014.