A strictly nonblocking 88 matrix switch was designed and fabricated using silica-based planar lightwave circuits (PLC) on a silicon substrate. The average insertion loss was 11 dB in the TE mode and 11.3 dB in the TM mode. The average switch element extinction ratio was 16.7 dB in the TE mode and 17.7 dB in the TM mode. The accumulated crosstalk was estimated to be 7.4 dB in the TE mode and 7.6 dB in the TM mode. The driving power of the phase shifter required for switching was about 0.5 W and the polarization dependence of the switching power was 4%. The switching response time was 1.3 msec. The wavelength range with a switch extinction ratio of over 15 dB was 1.31 µm30 nm.

This paper reviews the hyper-media photonic information network (HM-PIN) concept as a candidate of innovative future networks based on photonic technologies. The HM-PIN having a universal network interface integrates a variety of information services: telecommunications, newspapers, magazines, TV broadcasts and the growing collection of information servers. This network fundamentally offers three items: (1) bi-directional real-time channels with 10-Mbit/s-class or higher bit rate, (2) multipoint connections including multicasting/broadcasting, (3) high accessibility to information. These items are derived from the constraints of the conventional telephone networks and the Internet. By applying photonic technologies, the HM-PIN can be implemented as follows: The local network (the service platform) of the HM-PIN can be achieved by using a wavelength-division-multiplexing (WDM) broadcast-and-select (B&S) architecture that offers broadband multipoint connections (one-to-many, many-to-many) based on an inherent full-mesh topology. The WDM B&S local network will be able to support 10,000 to 100,000 channels (each with 10-Mbit/s or more bandwidth) by using optical and electrical multiplexing techniques. The backbone network can be constructed by combining photonic asynchronous transfer mode (ATM) switching systems and WDM transmission systems (including cross-connects). Two deployment scenarios of the HM-PIN (cost-oriented and service-oriented deployment scenarios) are also described for smoothly introducing the HM-PIN even before the cost issue is solved. The HM-PIN based on photonic technologies will be a future network service platform that greatly enhances communication services.

This paper describes a new free-space optical switch structure based on cascaded beam shifters (each consists of a liquid-crystal polarization controller array and a birefringent plate). This structure comprises 2-input, 2-output switching elements that are locally connected by links. It is applicable to a variety of switching networks, such as a Clos network. The switching network based on this structure is an analog switch that is transparent to signal format, bit rate, and modulation type, so it can handle various types of optical signals. Theoretical feasibility studies indicate that compact large-scale switches (i.e., 100-1000 ports) with relay lens systems can be implemented using beam shifters with a 0.4-dB insertion loss and a 30-dB extinction ratio. Experimental feasibility studies indicate that a 1024-cell beam shifter module with a 0.5-dB insertion loss and a 23-dB extinction ratio is possible at present. An alignment-free assembly technique using precise alignment guides is also confirmed. An experimental 8-stage, 1024-input 256-output concentrator shows low insertion loss characteristics (6.8dB on average) owing to the low-loss beam shifters and the alignment-free assembly technique. Practical switching networks mainly require the improvement of the extinction ratio of the beam shifter module and the development of a fiber pig-tailing technique. This switch structure is applicable to transparent switching networks such as subscriber line concentrators and inter-module connectors.

A photonic ATM switch based on wavelength-division multiplexing will include several lossy passive devices, erbium-doped fiber amplifiers, and semiconductor optical amplifiers (SOAs) in a cascade configuration for fast switching of ns order. Its level diagram, which is very different from those of optical transmission links, has not been adequately studied. This paper investigates the concept of basing the level design of the photonic asynchronous-transfer-mode (ATM) switch we are developing on its Q-factor. First, we derive formulation of the Q-factor in a single PD and a dual-PD in a Manchester-encoded signal, which has several merits in packet switching and that we believe will become popular in photonic packet switches. Using this formula, we show an example of the level-diagram design including the Q factor calculation in an optical combiner and distributor section without SOA in our photonic ATM switch. Next, we showed experimentally that the pattern effect in SOAs can be suppressed by using a Manchester-encoded signal. Finally, we confirm that the allowable minimum level diagram in the switch can be based on a simple Q calculation and easy measurement of a bit error rate (BER) in a back-to-back configuration when using a Manchester-encoded signal. These results show that basing the level design of photonic ATM switches on the Q factor is feasible when using a Manchester signals. This approach can be applied to various types of photonic packet switches.

This paper reviews the hyper-media photonic information network (HM-PIN) concept as a candidate of innovative future networks based on photonic technologies. The HM-PIN having a universal network interface integrates a variety of information services: telecommunications, newspapers, magazines, TV broadcasts and the growing collection of information servers. This network fundamentally offers three items: (1) bi-directional real-time channels with 10-Mbit/s-class or higher bit rate, (2) multipoint connections including multicasting/broadcasting, (3) high accessibility to information. These items are derived from the constraints of the conventional telephone networks and the Internet. By applying photonic technologies, the HM-PIN can be implemented as follows: The local network (the service platform) of the HM-PIN can be achieved by using a wavelength-division-multiplexing (WDM) broadcast-and-select (B&S) architecture that offers broadband multipoint connections (one-to-many, many-to-many) based on an inherent full-mesh topology. The WDM B&S local network will be able to support 10,000 to 100,000 channels (each with 10-Mbit/s or more bandwidth) by using optical and electrical multiplexing techniques. The backbone network can be constructed by combining photonic asynchronous transfer mode (ATM) switching systems and WDM transmission systems (including cross-connects). Two deployment scenarios of the HM-PIN (cost-oriented and service-oriented deployment scenarios) are also described for smoothly introducing the HM-PIN even before the cost issue is solved. The HM-PIN based on photonic technologies will be a future network service platform that greatly enhances communication services.

A photonic ATM switch based on wavelength-division multiplexing will include several lossy passive devices, erbium-doped fiber amplifiers, and semiconductor optical amplifiers (SOAs) in a cascade configuration for fast switching of ns order. Its level diagram, which is very different from those of optical transmission links, has not been adequately studied. This paper investigates the concept of basing the level design of the photonic asynchronous-transfer-mode (ATM) switch we are developing on its Q-factor. First, we derive formulation of the Q-factor in a single PD and a dual-PD in a Manchester-encoded signal, which has several merits in packet switching and that we believe will become popular in photonic packet switches. Using this formula, we show an example of the level-diagram design including the Q factor calculation in an optical combiner and distributor section without SOA in our photonic ATM switch. Next, we showed experimentally that the pattern effect in SOAs can be suppressed by using a Manchester-encoded signal. Finally, we confirm that the allowable minimum level diagram in the switch can be based on a simple Q calculation and easy measurement of a bit error rate (BER) in a back-to-back configuration when using a Manchester-encoded signal. These results show that basing the level design of photonic ATM switches on the Q factor is feasible when using a Manchester signals. This approach can be applied to various types of photonic packet switches.