2.55%. When slot is cut in the patch, the bandwidth increases to
2.78% however there is a slight mismatch (see Fig. 7). Further
when slotted patch is stacked with parasitic elements of the same
size the bandwidth of the patch further improves to 4.07% (see Fig.
8) and the matching also improves.
The variation of return loss with frequency for different value
of slot length and slot width is shown in Figures 9 and 10,
respectively. It is observed that the resonance frequency depends
inversely on both slot length and width and matching improves.
The variation of resonance frequency with substrate thickness h
1
and h
2
are shown in Figures 11 and 12, respectively. It is found
that resonance frequency depends directly on substrate thickness
h
1
where as it depends inversely on substrate thickness h
2
however
matching improves with increasing value of h
1
and h
2
.
5. CONCLUSION
It may be concluded that resonance frequency of the slot loaded
stacked patch is highly dependent on the slot dimensions as well as
parasitic element and substrate thickness (h
1
and h
2
).
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© 2008 Wiley Periodicals, Inc.
THE INFLUENCE OF THE ASE NOISE
ON THE CASCADABILITY OF ACTIVE
MACH-ZEHNDER INTERFEROMETER
SWITCHES
Jose Manuel Martinez, Javier Herrera, Francisco Ramos, and
Javier Marti
Nanophotonics Technology Centre, Universidad Politecnica de
Valencia, Camino de Vera, s/n. 46022 Valencia, Spain;
Corresponding author: framos@upvnet.upv.es
Received 4 February 2008
ABSTRACT: The influence of the ASE noise on the cascadability of
SOA-MZI structures is investigated. The experimental results show that
saturation effects in the SOAs are the main cause of signal degradation,
so counter-propagation pump schemes as well as lower bias currents
and optical powers are desirable when cascading several SOA-MZI op-
tical switches. © 2008 Wiley Periodicals, Inc. Microwave Opt
Technol Lett 50: 2529–2531, 2008; Published online in Wiley Inter-
Science (www.interscience.wiley.com). DOI 10.1002/mop.23737
Key words: optical switches; optical performance; semiconductor opti-
cal amplifiers; ASE noise
1. INTRODUCTION
The integrated active Mach-Zehnder interferometer based on semi-
conductor optical amplifiers (SOAs), commonly known as SOA-
MZI, is a flexible and powerful device in all-optical signal pro-
5 5.2 5.4 5.6 5.8 6
-25
-20
-15
-10
-5
0
Frequency (GHz)
Return loss (db)
h1=1.6 mm
h1=1.8 mm
h1=2.0mm
Figure 11 Variation of return loss with frequency for stacked disk
microstrip antenna for different thickness (h
1
)(h
2
2.5 mm, L 10 mm,
w 0.5 mm). [Color figure can be viewed in the online issue, which is
available at www.interscience.wiley.com]
5 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9 6
-30
-25
-20
-15
-10
-5
0
Frequency (GHz)
Return loss(db)
h2=2.5 mm
h2=3.0 mm
h2=3.0 mm
Figure 12 Variation of return loss with frequency for stacked disk
microstrip antenna for different thickness (h
2
)(h
1
2.5 mm, L 10 mm,
w 0.5 mm). [Color figure can be viewed in the online issue, which is
available at www.interscience.wiley.com]
DOI 10.1002/mop MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 50, No. 10, October 2008 2629