Mode Field Diameter Measurements
M. ARTIGLIA, G. COPPA, P. DI VITA, M. POTENZA,
Abstract-The role of the mode field diameter in the characterization
of single-mode fibers is examined. The most relevant definitions of this
parameter are reviewed and a comparative analysis of its measurement
methods is performed. Eniphasis is also given to the requirements posed
by the new fiber designs, such as the polarization-maintaining struc-
INGLE-MODE fibers (SMF) are being more and more
widely used in optical communication links, as they
offer very large bandwidths and low attenuations. After
the first generation of SMF, commercially available since
1982, a second generation of “special purpose” fibers has
recently followed, such as dispersion-shifted (DS) and
dispersion-flattened (DF) fibers
11, to meet the issues of
large transmission capacity over very long distances.
Moreover, to fully exploit the capabilities of coherent
transmission, a new family of optical fibers has been in-
which are able to preserve the state of polarization of the
propagating mode . A simple and effective characteri-
zation of the transmission properties of SMF’s has thus
become of paramount importance for system designers,
suppliers, and customers.
After a great deal of theoretical and experimental work
it has been found that for circularly symmetric fibers a
simple and useful characterization can be made by intro-
ducing the mode field diameters (MFD’s), parameters re-
lated to the optical field distribution in the fiber. In fact,
it has been shown that the MFD’s provide useful infor-
mation about the cabling performances of the guide, i.e.,
possible joint, macrobending, and microbending losses.
Moreover, if the MFD spectral behavior is known, the
fiber chromatic dispersion, which is related to the band-
width, can be obtained and the cutoff wavelength of the
first higher order mode can also be determined.
However, to obtain PM fibers, noncircular geometries
are to be used and therefore a suitable generalization of
the MFD concept is needed to characterize this new type
Manuscript received January 27. 1989: revised March 3. 1989.
M. Artiglia, P. Di Vita, and M. Potenza are with Centro Studi E La-
G. Coppa is with the Dipartimento di Energetica. Politecnico di Torino.
A. Sharma is with the Department of Physics. lndian Institute of Tech-
IEEE Log Number 8928819.
boratori Telecomunicazioni (CSELT), Torino, Italy.
nology Delhi, New Delhi.
of structures. This topic is at present a matter of discus-
sion both from a theoretical point of view and as far as
standardization procedures are concerned.
Up to now several different definitions of MFD have
been proposed. This work reviews the most meaningful
definitions and the corresponding measurement tech-
niques together with their applications. The definition of
the various MFD’s for circularly symmetric fibers will be
discussed first. Then the corresponding measurement
techniques will be described. Finally, the generalization