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Santur's strategy is to effectively integrate the most reliable technologies
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from the fields
of optics, semiconductor processing, electronics, and
packaging to provide value to our customers. Our specialty
is figuring out which combinations allow us to provide
high performance at reasonable cost. Distributed feedback
(DFB) lasers are the transmitters of choice for nearly
all longer distance telecommunication applications. Among
the many advantages of DFB lasers are their wavelength
stability and high power. Other tunable approaches frequently
give up this stability in order to obtain tuning. Non-DFB
based laser transmitters often are susceptible to mode
hops, degrade through life, and frequently cannot match
the power and the spectral performance.
The Santur DFB array is very similar in size and complexity
to the single element DFB chips prevalent in the industry,
but contains a number of lasers that allow the output
spectrum to be changed by selecting different elements
of the array. Our technology allows large numbers of DFBs
to be fabricated simultaneously, with high yield and identical
spectral shape, but at different and precisely determined
wavelengths. Quasi-continuous tuning that can access any
wavelength channel in the range can be obtained by selecting
the most appropriate DFB element in the array, and then
fine tuned using thermal or electro-optical means.
Arrays of DFBs are well known in the industry and have
been investigated by a number of different research groups
and organizations. What has previously prevented an efficient
use of an array for this application has been a simple
and low loss method of combining the outputs of the DFB
array into to the optical fiber. Typically integrated
star couplers are used that have a loss equal or greater
than the number of inputs. For example combining a laser
array with four elements with a passive star results in
a maximum throughput of 25%. Santur's technology, on the
other hand, can deliver nearly the entire output power
of all the lasers to the output, obviating the need for
additional components to amplify the power.
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Superimposed spectra
of complete module
with 13
dBm fiber coupled power.
(click image for enlargement) |
The 1000 series product line uses such a DFB array to
provide high fiber coupled power. Initial devices will
offer 10mW of optical power in the C-band for use with
an external modulator. Follow-on products include L-band
wavelengths and higher power. Integrated wavelength lockers
assure stability and registration to the ITU wavelengths.
The various components are hermetically packaged in an
industry standard butterfly package using passive low
cost techniques and combined with a compact electronic
controller board.
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