Masahiko Fujiwara

128 line photonic switching system using LiNbO/sub 3/ switch matrices and semiconductor traveling wave amplifiers

The possibility of a 128-line photonic space division switching system incorporating LiNbO/sub 3/ switch matrices and semiconductor traveling wave amplifiers (TWAs) is discussed. System design is considered in terms of the most suitable location for the TWA devices that gives the most practical power margin. Design requirements for a 128-line photonic switching system suitable for a small-sized private branch exchange requirement are presented along with experimental results. It has been shown that a five-stage switch cascade, suitable for such a high-capacity switching system with a power margin of greater than 5 dB in the highest switch loss situation is possible, using low-facet-reflection TWAs. Such TWA devices have been developed in the 1.3- mu m wavelength region with maximum fiber-to-fiber gain values of 15 dB. With maximum gain-polarization dependencies of 3 dB, switch losses can be compensated even under TM mode operation. >

Optical cross-connect system incorporated with newly developed operation and management system

The optical cross-connect (OXC) system described in this paper increases the operation flexibility and reliability of the trunk-line optical networks used for data communication. It features an OXC node comprised of a photonic switching network and a conventional electric switching network that are connected hierarchically. The operation and management scheme proposed for this OXC system uses the concept of an optical path and an optical section. The OXC system allows hitless network reconfiguration by switching the photonic switches gradually and without interference effects. An experimental OXC network showed that a broken optical path is restored, by rerouting, within 50 ms. Experiments using a LiNbO/sub 3/ 8/spl times/8 photonic switch matrix also showed that the OXC system provides photonic hitless switching. These results confirm the feasibility of flexibly reconfigurable and fast-restorable OXC systems.

A high-capacity photonic space-division switching system for broadband networks

A high-capacity (128-line) photonic space-division switching system prototype has been developed. All of the developments on polarization-independent LiNbO/sub 3/ matrix switches, semiconductor optical amplifiers for network loss compensation and three-dimensional optical interconnections for multi-stage switching networks combine to enlarge line capacity. The system is devised to provide both HDTV distribution services that require nonblocking connections and TV phone services that do not necessarily require these connections. It is confirmed that the system has been operating in providing 150 Mbps TV phone services and 600 Mbps HDTV distribution services with high stability. Thus, the system proves to be promising for STM broadband switching systems capable of providing high-speed continuous dense bit-stream services. The system, in concert with an ATM broadband switching system, could provide a full range of cost-effective broadband services from POTS (plain old telephone services) to HDTV. >

A coherent photonic wavelength-division switching system for broad-band networks

A coherent photonic wavelength-division (WD) switching system, utilizing a coherent wavelength switch ( lambda switch), is proposed. In the proposed coherent lambda switch, the tunable wavelength filter function is accomplished using coherent optical detection with a wavelength tunable local oscillator. The coherent photonic WD switching system has the following features; (1) low crosstalk switching for dense WDM signal, and (2) large line capacity capability. Design considerations show that 32 wavelength division channels can be available with a coherent lambda switch. It is also shown that a broadband metropolitan-area-network with over 1000 line capacity is possible, using a multistage connection in the coherent lambda switches. The switching function of the coherent lambda switch is demonstrated in a two-channel wavelength-synchronized switching experiment, using 8-GHz-spaced, 280-Mb/s optical FSK signals. >

Frequency separation locking and synchronization for FDM optical sources using widely frequency tunable laser diodes

A laser diode (LD) frequency separation locking method (called the reference pulse method) is proposed. This method has advantageous features for frequency division multiplexing (FDM) networks from the viewpoint of frequency separation stability with a strict frequency separation standard, modulation format independence, controllability over a large number of LDs, and frequency synchronization capability. Frequency locking experiments, using four and ten controlled LDs, confirmed that the control system using the method can stabilize frequency spacing for more than 100 LDs. The frequency fluctuation is suppressed to less than 10 MHz. Frequency synchronization, utilizing the reference pulse method, is proposed and demonstrated experimentally for two controlled LD groups, each consisting of three LDs. Frequency discrepancy between two LD groups was only 2.7% of the frequency separation. Required frequency-swept light power and controlled LD power at the detector input for frequency synchronization indicate that more than 50000 LD groups within a 10 km area, each having 100 LDs, can be synchronized simultaneously. >

Studies on semiconductor optical amplifiers for line capacity expansion in photonic space-division switching system

The problems associated with introducing traveling wave amplifiers (TWAs) to photonic space-division (SD) switching systems are examined. Experiments were carried out to clarify the TWA noise effect and interference between cascaded TWAs, using about 10-dB gain TWA modules. Possibility of a 128-line photonic SD switching system, using current polarization-independent LiNbO/sub 3/ 8*8 switch matrices, has been shown through the experiments. The possible line capacity value of the photonic SD switching system with TWAs is examined theoretically. It is shown that the expected line capacity value for such a switching system exceeds 10/sup 3/. >

A photonic wavelength-division switching system using tunable laser diode filters

A photonic wavelength-division switching system using semiconductor tunable wavelength filters is proposed. Wavelength switches and multistage switching networks are used. The potential of 100 wavelength-division channel achievement in switching systems is estimated, based on InP optical integrated circuits. A wavelength network synchronization method is proposed, which will enable the network to utilize such a large number of wavelength-division channels without wavelength misalignment and drift. An eight-channel wavelength-division switching experiment, using phase-shift controlled distributed-feedback laser diodes as tunable wavelength filters, is reported.<<ETX>>

Line Capacity Consideration for a Photonic Space-Division Switching System with Switch Matrices and Optical Amplifiers

Line capacity value for a photonic space-division switching system with optical amplifiers was theoretically examined, taking crosstalk and amplifier noise into account. The estimated line capacity value has been shown to exceed 103.

Design consideration for a coherent FDM-FSK dual-filter detection system with wavelength tunable DBR LD

Using coherent lightwave technology in an optical frequency division multiplexing (FDM) system has been widely investigated recently to achieve large- capacity optical networks.1 This paper studies channel capacity in a coherent FDM distributing service system (Fig. 1), considering the local oscillator tuning range (ch. 1 to ch.n) and the desired channel spacing (ch. 1 to ch.2). The optical FSK heterodyne dual-filter detection system is examined, because the FSK system is considered to be most practical from laser linewidth and modulation considerations.

Optical video/audio signal distribution network for a broadcast center using WD/TD/SD hybrid multiplexing

Todays TV broadcast centers require large capacity and flexible routing networks for handling uncompressed serial digital video signals. Fuji Televisions new broadcast center employs a newly developed optical video/audio signal distribution network This paper describes the design concept, the system structure, and the performance of the optical network. A wavelength-division and time division hybrid multiplexed (WD/TD) optical network has been applied to the broadcast center. This type of optical network is attractive for a broadcast center application, because of its large capacity, multiple format handling, and flexible operation capabilities.