With the foreseen growth of communication capacity, further capacity and flexibility enhancements are required for future transport networks. Photonic switching is expected to be a key technology to solve the potential bottleneck, which could be found in transport network nodes. This paper first explains the "Optical Fiber Freeway" concept, as an example of future transport networks. Following this, the possible optical transport network structure using photonic switching technologies, for realizing the Optical Fiber Freeway concept, is explained. An Optical CrossConnect (OXC) and optical Add/Drop Multiplexer (ADM) are key components. Examples of recent development of photonic switching systems toward these targets are also reviewed. An OXC using photonic Space-Division (SD) switching technology has been proposed and demonstrated. This type of OXC will realize flexible reconfiguration and optical hitless switching, and it can meet the introduction of Wavelength Division Multiplexing (WDM) technique. Line failure restoration operation at 2.4Gb/s has been successfully demonstrated. An optical packet network with a slotted ring/bus structure using a wavelength address technique has been proposed as a packet/cell based optical ADM. The experimental system employs a practical media access control system as well as a fast-wavelength switched transmitter suppressing thermally induced wavelength drift. Cell communication at 622Mb/s has been demonstrated with the experimental system. These results show that hardware technologies have been developed steadily. With a future study on an all optical network management scheme, a high capacity and flexible optical network would be realized.

The photonic Space-Division (SD) switching network is attractive for constructing flexible broadband networks. This paper first describes possible applications of the network. A broadband STM switching system, Digital Cross-connect System (DCS) and Video signal distribution switch, especially for HDTV signals, are attractive near term applications. Recent activities on photonic SD switching network developments aiming at these application are also reviewed. A 128 line prototype switching system has been developed. This system utilizes LiNbO3 photonic switch matrices, semiconductor traveling wave amplifiers (TWAs) and three dimensional optical interconnections for multi stage switching networks. It is confirmed that the system has been operating in providing 150Mb/s TV phone services and 600Mb/s HDTV distribution services with high stability. An experimental optical Digital Crossconnect System (optical DCS) has also been demonstrated. Line failure restoration operation at 2.4Gb/s has been successfully demonstrated. These experimental demonstrations prove that practical photonic switching systems are feasible with current technologies.