Photonic Network Communications, 3:4, 327±333, 2001
# 2001 Kluwer Academic Publishers.Manufactured in The Netherlands.
A Taxonomical Consideration of Optical Add/Drop Multiplexers
Cedric F.Lam,* Nicholas J.Frigo
AT&T LabsÐResearch, Room A5-1E31, 200 S. Laurel Ave., Middletown, NJ 07748, USA
E-mail: c¯firstname.lastname@example.org, email@example.com
JDS Uniphase, 625 Industrial Way West, Eatontown, NJ 07724, USA
Received April 2, 2001; Revised June 15, 2001
Abstract. The use of optical add/drop multiplexers (OADMs) is considered as a possible way to save the number of transponders required at a
network node by optically bypassing wavelengths that do not need to be dropped.There are many different ¯avors of OADMs offered by
vendors.In this paper, we give a taxonomy of OADMs from the perspectives of both technology considerations and possible implications on
network performance.The purpose of the taxonomy is to serve as a frame work for cost and performance studies on dense wavelength division
multiplexing (DWDM) optical transmission systems.
Keywords: optical add/drop multiplexer, taxonomy, wavelength division multiplexing
We ®rst give a brief presentation of optical add/drop
multiplexers (OADMs) from the physical technology
point of view.Basically, three contending technolo-
gies, multi-layer thin-®lm interferometric ®lters, ®ber
Bragg gratings and arrayed waveguide routers (AWG;
also called waveguide grating routers or Dragone
routers after inventor C.Dragone) are viewed as
having promising market potentials.
In the next section, we summarize the properties of
the above three major technologies as general back-
ground knowledge to facilitate understanding the
limitations and design considerations in OADM
systems.However, the main purpose of this document
is to serve as a taxonomy of OADMs from a functional
point of view, and provide a general framework for
further network system design and performance
2 Technology Background
Among the three major contending options, thin ®lm
®lters  can be made relatively cheaply.It is also
commonly used to achieve bandpass ®lters, which
cover the spectrum occupied by a few wavelengths in
a dense WDM system having ITU wavelength
separations from 25 GHz to 200 GHz.Thin ®lm ®lters
have the advantages of low loss, low polarization
dependence, and most importantly, very good thermal
stability, which makes them ideal for ®eld applica-
tions in low cost systems in which temperature control
is undesirable for cost reasons.
Technology advancement in the recent years has
made it possible to produce low loss, narrow-band
thin ®lm ®lters with very sharp roll off and relatively
¯at passband (e.g., + 0.11 nm BW with 20±30 dB
suppression at 0.5 nm from the passband center)
which meets the 100 GHz ITU DWDM requirements.
* Corresponding author.