O A

1633
Journal of Applied Sciences Research, 7(11): 1633-1639, 2011
ISSN 1819-544X
This is a refereed journal and all articles are professionally screened and reviewed
ORIGINAL ARTICLES
Parallel Connected Optical Add Drop Multiplexer (PC-OADM) Extend the Features of
Optical Communication System
Mohammad Syuhaimi Ab-Rahman
Spectrum Technology Research Group (SPECTECH), Department of Electrical, Electronic and Systems
Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, 43600 Bangi,
Malaysia, 43600 Bandar Baru Bangi, Selangor.
ABSTRACT
With the recent development of optical networks require a variety of new features of which are security and
reliability. Since the information carried by the optical carrier is too large requires features that ensure the signal
is always up to the user even in damage whatsoever. To meet up the rapid development will require further
improvement in existing optical devices such as OADM. This paper proposes improvements in the function of
OADM devices by combining these two devices in parallel. The results obtained allow the ring network perform
the function of redundancy and migration. Thus increasing the reliability of an optical network. At the end of
this paper we compared the characteristics of the device OADM, OXC, TRN, OXN, OXADM and Parallel
Connected OADM (PC-OADM).
Key words:
Introduction
Optical network SDH/SONET consists of two main architectures. The first architecture combines the
electrical and optical technologies that involve the conversion of the domain on the signal received from the
core to be distributed to the customer premises. Network architecture is known as hybrid SDH/SONET. The
second architecture uses fully optical technology which terminating all of electrical based devices and make the
network very easy by the presence of only a few elements which are optical cross connect (OCS) and optical
core switch. This architecture is called network optical SDH / SONET.
Hybrid SDH/SONET Network involves the replacement of the device B-DCS and W-DCS to OCS devices.
ADM is still used as a terminating element and add/drop signals. ADM is still working in the electrical domain
which receive signals in the optical domain and convert it to electrical domain and convert it again in the optical
domain to be sent to the device OCS. Since ADM is still working in the electrical domain induces the
phenomenon of the bottleneck between the main core network and the distribution (RHK, 2003). Hence the
need of such devices that can function in the optical domain completely necessary. However, the first stage is
still used in today's world of communications and ADM device is still sold in international markets.
Optical SDH/SONET network pointing towards full implementation of the optical fiber that incorporates or
apply all the functions carried out by ADM in the OCS. Besides as a switch directing the signal path, OCS in
this architecture is also capable of carrying out the functions to add/drop (RHK, 2003). All signal processing
performed in the optical domain. The second stage of development is too fast and many new optical devices
have the same functions and features but value added with functions that make it so special compared to
competing devices. The device which is variable ring nodes (TRN), optical cross-connect nodes (OXN), optical
cross-connect system (OCCS), Arrayed Waveguide Grating Multiplexer (AWGM), MEMS cross-connect
systems (MEMX), optical cross connect (OXC), Add drop optical multiplexing (OADM) and Optical Cross Add
and Drop Multiplexer (OXADM).
Corresponding Author: Mohammad Syuhaimi Ab-Rahman, Spectrum Technology Research Group (SPECTECH),
Department of Electrical, Electronic and Systems Engineering, Faculty of Engineering and Built
Environment, Universiti Kebangsaan Malaysia, 43600 Bangi, Malaysia, 43600 Bandar Baru
Bangi, Selangor.
E-mail: [email protected]
1634
J. Appl. Sci. Res., 7(11): 1633-1639, 2011
Existing Device Comparison:
OADM:
Number of Single Input Terminal to Limit the Application:
OADM is fundamental design for the new devices development such as TRN, ROADM and others.
However there is also a resource that mentioning OADM is also used in metropolitan ring network as a optical
node (Kataoka et al., 2004; Nuzman et al., 2003). OADM has basic architecture consists of one input terminal
and one output terminal only causes one working line that can be used a ring network system. The absence of
the second line (stand by line) resulting in the restoration scheme offered by the OADM, while still minimal.
However, the wavelength drop and segmentation mechanism can be used in the event of damage to isolate the
breakdown and active area.
Rise of TRN and OXN:
After technology SONET SDH has been replaced by full optical technology which involving the
replacement of major components of the ADM to the OCS. OCS-based OXC devices have been used as the first
device that integrate the functions of B-DCS, W-DCS and ADM on a single device. However, the initial OCS
device is not equipped with several new features and a unique addition to the basic functions of the three devices
mentioned above. However, with increasing demands on data transmission rates are too high and the types of
operational data causes the need for some new features such as monitoring, security and the multiplex to
integrate with the device. This has led to the emergence of new devices as a second generation to meet the
requirement of current optical networks by means of TRN and OXN.
TRN device was developed on the basis of OADM which consist of optical add and drop elements. TRN
was introduced by Louay Eldada and Joris van Nunen (2000) from Telephotonic Inc.. With the additional
features of routing has able the signal to be directed to any output path. TRN also allows data transmission in
both directions and use both routes as a data transmission path. TRN is equipped with a number of key functions
such as (Eldada and Nunen, 2000):
1. Add and drop.
2. Routing (path switch).
3. Linear protection for dedicated protection Schme (OCh-DPRing).
4. Ring protection for Shared Protection Scheme (OMS-SPRing).
OXN device was developed based on the OXC device which consist of path switch elements (crosslinking).
To ensure stability and precision of the wavelength of operation, variable Bragg grating device used to select the
wavelengths into either input terminal to cross-connect to other bases or to be dropped. OXN was introduced by
Edward Helsinky Mutafungwa from the University of Technology in 2001 (Mutafungwa, 2001). OXN is
developed for all topology of the point to point (P2P), ring and mesh. So this OXN said to be more flexible and
suitable for use in topology migration (from ring to mesh) particularly where it is equipped with security scheme
for both these topologies. OXN can be used for bidirectional data transmission using the two routes as the route
of data transmission. OXN is equipped with a number of key functions such as (Mutafungwa, 2001):
1. Path switch.
2. Add and drop.
5. Linear protection for dedicated protection Schme (OCh-DPRing).
3. ‘Multiplexing’ for mesh and ring topology.
The ‘Multiplexing " in OXN it essentially different from the OXC device. This feature is a security scheme
for mesh network topology. In a ring topology, the feature is used as a protection scheme for bidirectional path
switched ring network (BPSR).
Rise of OXADM:
Rahman et al., (2006a) has introduced a new architecture of asymmetrical optical switch device which is
expected to have vast application in optical communication and monitoring system. It has many excellent
features such as low crosstalk, lossless and multifunction. The multifunctional device means the integration of
single functional devices onto single architecture and Optical Cross Add and Drop Multiplexer (OXADM)
achieved the point with its unique architecture. With the use of micro-electro-mechanical systems (MEMs)
technology has minimized the effect of crosstalk and return loss. With the accumulation feature, asymmetrical
OXADM has widened its application to fiber-to-the-home (FTTH) and network security system (Ab-Rahman et
al., 2006d)(Ab-Rahman, 2010a)(Ab-Rahman and Jumari, 2009a)(Ab-Rahman et al., 2009b. The main function
1635
J. Appl. Sci. Res., 7(11): 1633-1639, 2011
of OXADM is to reconfigure the optical channel path while implementing add and drop function
simultaneously. The multifunctional OXADM can also works as single optical devices such as multiplexer,
demultiplexer, optical cross-connect (OXC), optical add drop multiplexer (OADM), wavelength selective
coupler (WSC) and wavelength roundabout (WRB) (Ab-Rahman and Wahab, 2008a)(Ab-Rahman, 2011a).
With such the excellent features, the OXADM is expected to be unique, universal and with a high reliability that
is used to overcome the various functions in wavelength-division multiplexing (WDM) communication network
today.
Increased capacity data transmission device in a ring network and enables the network to migrate to other
topologies such as mesh (Ab-Rahman and Shaari, 2006c) (Ab-Rahman and Shaari, 2007b). At the same time
protection features are introduced. In which three security schemes are introduced; the linear protection,
multiplex protection (Ab-Rahman, 2008b) and ring protection. However, the analytical study has proved the
OXADM has constrained in scalability features. The result showed the scalability number is twice lower than
OXC device (Ab-Rahman et al., 2006b)(Ab-Rahman et al., 2010b). OXADM has also offer low insertion and
suitable to be in any transmission rate system in mesh and ring optical network (Ab-Rahman 2011b)(AbRahman 2011c).
Parallel Connected OADM (PC-OADM):
The schematic of PC-OADM is shown in Figure 1. Two OADM devices are connected in parallel that are
connected using drop and add port. 2x2 switch is installed in the middle to direct the appropriate path based on
requirement. There are two conditions that offered; the path change/switch and U-turn mechanism. Path
switching is necessary to be able to activate the linear protection scheme and ‘U’ turn mechanism is very
important for the protection ring mechanism. Both features are important and clearly stated in (Ab-Rahman et
al., 2007c) (Ab-Rahman, 2008c). However multiplexing protection function cannot be done by using this
architecture.
Fig. 1: Schematic of PC-OADM (a). Performing function of path switch (b) ‘U’ turn mechanism (c).
Protection Architecture:
In a ring network, each node is connected via two-line transmission line which are working and protection
lines. Any damage or degradation in signal quality at working line will switch the traffic to the line protection.
Distribution node is responsible for handling restoration mechanisms through automatic protection switching
(APS), which function to prevent network failures and ensure the transmission of signal quality.
Generally, two types of restoration scheme can be applied (Acterna Corp. 2005):
1636
J. Appl. Sci. Res., 7(11): 1633-1639, 2011
a) Linear Protection - linear multiplex section protection, linear MSP) according to ITU-TG.783 and ANSI
T1.105.1 for point to point configuration).
b) Ring protection -multiplex section shared protection ring, MSSP ring according to ITU-TG.841 and ANSI
T1.105.1 for ring configuration.
Case 1: Linear Protection:
Figure 2.10 shows the architecture of the linear protection of the MAN ring network operated by the PCOADM. PC-OADM function to convert the data transmission path during the line breaks work using 1:1
protection mechanism. The signal will be diverted to the original route as soon as the damage been repaired.
Here the damage occurred will be detected by sensors installed on the line and the signal will be sent to the
microprocessor system through the bytes K1 and K2. This microprocessor system then activates the system
switches on the device to change the route. Detection and repair mechanism is called APS.
Case 2: Ring Protection:
In the event of failure to the two lines or even on the optical nodes, ring protection architecture will be used.
Node near the failure will function to connect the working line to protection to form a new structure of ring
network. PC-OADM switch will ensure continuity of operation of the two rings if there is a damage the device
in a ring topology network. It is used to prevent segmentation to separate the the failed station from optic
network. The operating is similar to the OBS used in the FDDI protocol, but the difference is that the switch was
developed separately by the concentrators and installed in front of each concentrators system, in contrast to PCOADM where the switch E is an element in the device is activated on the node close to damage point. PCOADM repair mechanism is suitable for use in fiber-optic system completely (all optical based system) that
operates without a change in the domain (optical-electronic-optical) differ as the OBS for FDDI and Ethernet
protocols.
Fig. 2: Exchange data path in a network that is controlled by a switch if one line is damaged to perform linear
protection scheme (Keiser, 2000).
Flexibly Node for Optical Communication Network:
Since OC-OADM have the same capabilities with a combination of two optical devices which OXC and
OADM, it is suitable to be placed in any type of topology in optical communications networks. Accordingly, it
is able to function as a flexible optical nodes in the restructuring topology that occurred in a metropolitan
network. In the process of topology change such as a ring configuration to the mesh configuration, installing to
new device and network modifications do not need to be done for this PC-OADM due to its function in both of
these topologies. This is in contrast to the case of TRN and OADM are not able to function as a node in a mesh
topology. If the modifications carried out, the devices should be replaced with other devices either OXC or even
OXN. So this PC-OADM is said to be a flexible optical node that is able to accommodate any changes in the
structure of the original topology used in an optical communications network. Figure 2.12 shows the
restructuring of metropolitan optical networks from ring topologies to mesh topologies that use PC-OADM as
optical nodes. The features is also similar offered by OXADM (Ab-Rahman and Shaari, 2007a)(Ab-Rahman et
al., 2008d)(Ab-Rahman et al., 2011d).
1637
J. Appl. Sci. Res., 7(11): 1633-1639, 2011
Fig. 3: Closing the data path in a network that is controlled by PC-OADM switch in case of an emergency
involving damage to the node or cable transmission. This architecture is called a ring protection
(Keiser, 2000).
Fig. 4: The restructuring of the topology of a ring to mesh topologies in metropolitan communications network
using a node optical OXADM (Comellas et al., 2004).
Existing Device Comparison:
Our proposed device has been compared with the other existing devices such as OADM, OXN, TRN, OXN
and OXADM. Table 1 shows the comparison of PC- OADM with the other existing devices. Although the PCOADM doesn’t offer many features as OXADM but it is competitively to the other devices based on the
parameters that have been compared. Moreover, PC-OADM is much lower cost as compare to other new
generation devices such as TRN, OXN and OXADM. The insertion loss comparison for every function in
OADM, OXC, OXADM and PC-OADM is depicted in Figure 5.
Table 1: Features comparison between first generation devices and second generation devices.
Feature
OADM
OXC
TRN
OXN
OXADM
(PC-OADM)
Multiplex Protection
X
X
√
√
√
X
Linear Protection (1:1)
X
X
√
√
√
√
1638
J. Appl. Sci. Res., 7(11): 1633-1639, 2011
Ring Protection
Ring to Mesh Migration
Topology
Symmetrical Architecture
X
X
√
X
√
√
X
√
X
√
√
√
Ring
Mesh
Ring
Ring and Mesh
Ring and Mesh
Ring and Mesh
√
√
√
√
X
√
Fig. 5: Insertion Loss for a various function in OADM, OXC, OXADM and PC-OADM.
Reference
Ab-Rahman, M.S., H. Husin, A.A. Ehsan and S. Shaari, 2006b. Analytical modeling of optical cross add and
drop multiplexing switch. In: ICSE IEEE International Conference on Semiconductor Electronics. IEEE
Malaysia Section, pp: 290-293.
Ab-Rahman, M.S., 2008b. Highlighting on Multiplex Restoration Scheme in Optical Cross add and Drop
Multiplexer (OXADM). Journal of Optical Communication, JOC (German), 29(4): 205-208.
Ab-Rahman, M.S., 2008c. First Experimental on OXADM restoration scheme Using Point-to-Point
Configuration. Journal of Optical Communication, JOC (German), 29(3): 174-177.
Ab-Rahman, M.S., 2010a. Protection for Tree-Based EPON-FTTH Architecture Using Combination ACS and
OXADM. Australian Journals of Basic Applied Science, 12(4): 6260-6268.
Ab-Rahman, M.S., 2011a. The Novel of Multifunctional Features of Optical Cross Add and Drop Multiplexer
(OXADM) Device. Journal of Applied Sciences Research. Accepted.
Ab-Rahman, M.S., 2011b. Determination the Achievable Distance of Optical Cross Add and Drop Multiplexer
(OXADM) Point-to-Point Network. Journal of Applied Sciences Research, 7(5): 590-594.
Ab-Rahman, M.S., 2011c. Performance Analysis of Optical Cross Add and Drop Multiplexer (OXADM) Device
in Different Transmission Rate. Journal of Applied Sciences Research, 7(5): 595-599.
Ab-Rahman, M.S., A.A. Ehsan, H. Hussin, M.F. Bukhori and S. Shaari, 2007c. Optical Cross Add and Drop
Multiplexer (OXADM) in CWDM Ring Network, Journal of Optical Communication, JOC (German). 28(3):
201-205.
Ab-Rahman, M.S. and S. Shaari, 2007b. Survivable Mesh Upgraded Ring in Metropolitan Network, Journal of
Optical Communication, JOC (German), 28(3): 206-211.
Ab-Rahman, M.S., A. Premadi, H. Fadziati and S. Shaari, 2011d. Flexible Topology Migration in Optical Cross
Add and Drop Multiplexer Metropolitan Ring Network - The Next Proposal. Information Technology
Journal, 10(6): 1258-1263.
Ab-Rahman, M.S., A.A. Ehsan and S. Shaari, 2006c. Mesh upgraded ring in metropolitan network using
OXADM. In: 5th ICOCN/ATFO International Conference on Optical Communications and Networks and
the 2nd International Symposium on Advances and Trends in Fiber held at Chengdu, China, pp: 225-227.
Ab-Rahman, M.S., A.A., Ehsan and S. Shaari, 2006d. Survivability in FTTH PON access network using optical
cross add and drop multiplexer switch. Journal of Optical Communication (JOC), 27(5): 263-269.
Ab-Rahman, M.S. and H.F.A. Wahab, 2008a. Development of optical multifunctional switch. In: 2nd
HUT_ICCE International Conference on Communications and Electronics held at Vietnam, p: 454-460.
Ab-Rahman, M.S. and K. Jumari, 2009a. The Proposal of OXADM Application in FTTH Network. Journal of
Optical Communication, JOC (German), 30(2): 99-103.
1639
J. Appl. Sci. Res., 7(11): 1633-1639, 2011
Ab-Rahman, M.S., L.Y. Siong, C.C. Khuen, L.W. Kit and T.W. How, 2010b. Power Penalty Assessment of
OXADM Device Model - Analytical Analysis. Journal of Optical Communication, JOC (German), 31(4)pp:
245-249.
Ab-Rahman, M.S., N.M.A.A. Amir and S.A.C Aziz, 2009b. Analytical Analysis of Cascaded OXADM in
Survivability Scheme for Tree-Based EPON-FTTH Immediate Split Architecture. Australian Journals of
Basic Applied Science, 3(3): 2706-2715.
Ab-Rahman, M.S. and S. Shaari. 2006a. OXADM restoration scheme: approach to optical ring network
protection. In: ICON IEEE International Conference on Networks held at Singapore, pp: 371-376.
Ab-Rahman, M.S. and S. Shaari 2007a. Survivable Mesh Upgraded Ring in Metropolitan Network. Journal of
Optical Communication (JOC), 28(3): 206-211.
Acterna Corp, 2005. Efficient testing of synchronous rings. http://www.acterna.com/global/products/ANT/.
Eldada, L. and J.V. Nunen, 2000. Architecture and performance requirements of optical metro ring nodes in
implementing optical add/drop and protection functions. Telephotonics Review.
Kataoka, N., N. Wada, F. Kubota and K. Kitayama, 2004. 40 Gbps packet-selective Photonic add/drop
multiplexer based in optical code label header processing. Journal of lightwave Technology, 22(11): 23772385.
Mutafungwa, E., 2000. An improved wavelength-selective all fiber cross-connect node. IEEE Journal of
Applied Optics, pp: 63-69.
Nuzman, C., K. Kumaran, N. Nithil and I. Saniee, 2003. Effects of modularity and connectivity on OADM
deployment in ring networks. Optical Fiber Communication and Exhibit OFC, 03(1): 360-361.
RHK Inc., 2003. Metro Core Network Evolution: Integration reduces costs, adds service flexibility.
http://www.rhk.com.