Optical Hub Network –proposal and implementation-
Aoyama Gakuin University, 5-10-1 Fuchinobe Sagamihara-shi Kanagawa-ken Japan 229-8558
E-LambdaNet Corporation, 2-12-24 Yaei Sagamihara-shi Kanagawa-ken Japan 229-0029
Abstract: city area networking to play a major role in Japan.
FTTH is now being rapidly introduced in Japan. NTT is
planning to demonstrate NGN test services. Neither service 3. DESIGN ISSUES
meets Cyber Hospital requirements. We are a co-operative
working group combining two universities and a small venture Conventional FTTH, i.e., PON system has the
company. Working with a research grant from MIC (Ministry following issues to be solved.
of Internal Affairs and Communications), we are now (1) Media access methods are not equal for all users as
developing a fiber based high speed network tentatively named we see in Ethernet, so system enhancement depends on a
the “Optical Hub Network”. Requirements, specification, carrier’s investment.
network operation and test bed data are described.
(2) PON applies a time-share scheme and it is strictly
controlled from the head end. This means it limits the
1. INTRODUCTION flexibility for communication speed selection, that is, a
The purpose of the Optical Hub Network is to
client cannot select communication speed.
implement a new type of city area network using dark
(3) Where a large capacity link is required, CWDM
fibers, and to provide a service which until now has been
technology is applied to a FTTH fiber because the cost is
difficult to provide with FTTH or NGN. We expect it
considered reasonable. But, a new light wave channel
will be a good example of a city or metropolitan area
has been added independently from the PON scheme. So
network infrastructure in the near future.
a PON system that has the possibility of plural wave
Our group is composed of three members: a technical
channels selection has not yet been introduced
department of Aoyama Gakuin University, a medical
commercially. This results in a PON client’s
system research department of Kitasato Medical
communication capacity increase being limited.
University and a small venture company: E-LambdaNet
Our proposed Optical Hub Network meets the challenge
of solving these issues using the following design
The specification requirement comes from the medical
university. Japan is now facing an increasingly aging
(a) Introduce an equal media access scheme via an
population. The national social security budget is
Optical Hub which delivers all optical inputs to all
increasing every year, so improved hospital services are
required. The medical university has a plan to implement
(b) The network scale could be extended by applying
a so-called Cyber Hospital. The idea is to have
plural Optical Hub connections. This requires the
networking among several big main hospitals and many
introduction of SOA to compensate optical signal losses.
small hospitals over one city area “Sagamihara-city”
(c) CWDM or DWDM is introduced to provide high
where two universities are located.
(d) The Optical Hub Network has two access modes, i.e.,
DA (Dedicated Access) and MA (Multiple Access).
If a small hospital can have better medical advice from
(e) The MA mode allows all terminals to share the
a medical specialist group working in a big hospital, it
Optical Hub Network based on the Ethernet
will contribute to improved medical services. The
question is what types of network services are required.
(f) The DA mode assigns a connection between terminals
Here are three vital areas:
by means of a time slot and a wavelength allocation.
(1) High volume medical contents should be smoothly
transferred through a network.
(2) Low latency network transmission for a high
4. TEST BED DESIGN
The test bed (named APN2; Aoyama Gakuin Univ.
definition digital camera moving images.
Network2) has four routers interfacing with our campus
(3) High speed radio transmission to a hospital from an
network. The purpose of an overlay network structure is
to carry high bit rate streams such as HDV on APN2, and
To solve these problems, applying the up-coming
internet access via the campus network. The router,
NGN service might be one solution. For the moment,
located between APN2 and the campus network,
however, a hospital system application is not expected as
identifies these traffic types for routing. So APN2 routers
an NGN killer application. It seems that no NGN
run by FreeBSD and some part of the routing algorithm
services provider is currently expecting such high speed
has been modified. Still we need further research for a (7) DA allows access to a slot where access is dedicated
better routing operation. The APN2 framework is as to a pair of ONICs by TWM.
follows: The Optical Hub Network is physically an optical
(1) An Optical Hub Network has 2 key components: an broadcast network. The Test Bed applies 1000BASE-T to
Optical Hub (OHUB) and an Optical Network Interface provide both broadcast and unicast services on it by
Card (ONIC). For the moment, this is a box rather than a means of an ONIC control.
(2) The test bed has one OHUB and four ONICs. Four 5. TEST BED RESULTS
ONICs are connected to each other via an OHUB and We have confirmed that two types of DA connections,
optical fibers as Figure 1 shows. i.e., the high speed transmissions are available as Figure
(3) The OHUB has 4 in-ports and 4 out-ports. One light 1 shows.
signal entered to an in-port is distributed equally to 4 (1) HDMI transmission
out-ports as Figure 2, right, shows. (2) HDV IEEE1394 transmission
(4) The ONIC has the functions of E/O, O/E, and We are half way to implementing MA connection.
input/output electronic signal line selection. It also has a The key issue which limits the network capacity is the
function of a timeslot and wavelength allocation for optical signal loss budget. The design parameters are as
OHUB fiber lines. For the test convenience, the follows.
allocation order comes from Scheduler which provides a -OHUB has 4 ports. Insertion loss=12dB
time and wavelength matrix to ONIC. -ONIC LD; Pout=0.0 to 5.0 dBm,
-ONIC PIN-PD Pmin< -18dBm
The Test Bed operation is designed as follows: So, a one stage OHUB connection between ONICs
(1) There are two domain axes: “time” and “optical wave does not require optical signal amplification.
length”. Here, the minimum switching time between When we consider tandem connection of OHUBs, an
timeslots is one millisecond. Time synchronization is optical amplifier is indispensable for OHUB. We are
controlled by having a GPS 1ms signal when necessary. currently evaluating SOA capability . Our tentative
Four wavelengths, 1.53, 1.55, 1.57, 1.59 microns, are data shows it has approximately 20dB gain. Further
selected from a CWDM. Each wavelength has the study is necessary for successful Optical Hub Network
capacity for 2.5Gbps transmission. design.
(2) When the ONIC receives an information transfer
request from a client terminal, it selects one available 6. CONCLUSION
slot between a source ONIC and a destination ONIC. We have proposed an Optical Hub Network. It consists
The slot could be one wavelength, one time slot, or a of two major components, an Optical Network Interface
Card and an Optical Hub. Our Test Bed APN2 is
combination of time and wavelength. presented in terms of a network structure and an
(3) Here “the time and wave matrix (TWM)” is the key operation design. It has two access modes, multiple
network routing information, i.e., it allocates Optical access (MA) and dedicated access (DA). APN2 is now
Hub Network resources for all source/destination possible to demonstrate two types of high speed stream
connections. transmission. The critical design parameter is the optical
loss budget and we are working on how to apply SOA to
(4) In the case of the Test Bed, TWM is given from solve the problem.
Scheduler at present. We plan to implement a distributed
processing algorithm as the Ethernet provides ARP REFERENCES
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(5) The Test Bed has MA and DA modes. “Amplified CWDM Systems”, Proc. Lasers and Electro-Optics
Society Annual Meeting 2003, vol.2, pp.678-679
(6) MA is an access to a slot where multiple ONICs are M.Akiyama, K.Tada, J.Mizusawa ”Photonic Switching
allowed access. Access control is performed on an System”, IEICE. Trans. Vol.E74. No.1, pp84-92,1991
optical level at ONIC fiber input/output. So an optical Acknowledgement: This research is funded by SCOPE
signal does not transfer on a fiber between (Ministry of Internal Affairs and Communications, Japan
ONICs/OHUB when no data signal transmission is