Optical: systems and elements – Optical amplifier
Reexamination Certificate
2002-10-02
2004-04-27
Hellner, Mark (Department: 2877)
Optical: systems and elements
Optical amplifier
C356S073100
Reexamination Certificate
active
06728025
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor optical amplifier characteristic evaluation method and apparatus and, more particularly, to a characteristic evaluation method for a semiconductor optical amplifier (to be referred to as an SOA hereinafter) used in an optical transmission system for optical communication, optical switching, optical signal processing, or the like.
An optical transmission system using light for optical communication, optical switching, optical signal processing, or the like uses various kinds of optical devices. In such an optical transmission system, an optical loss poses a serious problem, and therefore, it is indispensable to compensate for an attenuated optical signal using optical amplifiers. Of optical amplifiers essential in an optical transmission system, an SOA is compact and highly efficient. A semiconductor optical amplifier is very promising because it can be hybrid-integrated with a planar lightwave circuit (PLC) constituted by a quartz-based optical waveguide.
To use SOAs in optical transmission systems, they must undergo chip evaluation to screen non-defective units before hybrid mounting or module mounting.
For such screening, an SOA characteristic evaluation apparatus as shown in
FIG. 10
is conventionally used.
FIG. 10
shows the schematic arrangement of the characteristic evaluation apparatus. As shown in
FIG. 10
, the conventional SOA characteristic evaluation apparatus comprises a multi-wavelength optical source
101
for emitting multi-wavelength light, a wavelength selection switch
105
for selecting a specific wavelength from the multi-wavelength light emitted from the multi-wavelength optical source
101
, an optical attenuator
106
for adjusting the optical intensity, a polarization controller
102
for generating various polarized states, optical power meters
104
and
108
for monitoring output light (amplified spontaneous emission or ASE) from an SOA
115
, an optical circulator
103
, a coupler
107
, a wavelength filter
109
for screening a wavelength, and an optical power meter
110
for measuring the optical intensity. These components are connected using optical fibers.
To evaluate the characteristic of the SOA using the apparatus shown in
FIG. 10
, first, optical fibers
113
and
114
are aligned to the two ends of the SOA
115
while monitoring, by the optical power meters
104
and
108
, output light (amplified spontaneous emission or ASE) from the SOA
115
to be evaluated.
After the optical fibers
113
and
114
are aligned, the wavelength selection switch
105
selects a specific wavelength from multi-wavelength light emitted from the multi-wavelength optical source
101
. The optical attenuator
106
adjusts the optical intensity. The polarization controller
102
controls the polarized state. The light is thus guided to an end face of the SOA
115
through the optical fiber
113
. The external light is thus input to the SOA
115
.
On the other hand, the optical power meter
110
measures the optical intensity of input/output light from the SOA
115
, which is guided to the wavelength filter
109
through the optical fiber
114
and undergoes noise component removal by the wavelength filter
109
.
In this state, the polarization controller
102
generates various polarized states. The absolute value of the gain of the SOA
115
can be calculated from the measurement value by the optical power meter
110
at this time. In addition, the dependence of the gain on polarization can be measured by measuring the maximum or minimum value of the optical intensity by the optical power meter
110
.
For semiconductor lasers having a structure similar to an SOA, the elements are evaluated on the basis of the current vs. optical output characteristic (I-L characteristic) by pulse driving in order to remove the influence of heat.
For the SOA
115
, however, since light is input to it through the optical fiber
113
, the amplified optical intensity of the external injection light decreases due to the fiber coupling loss at the two ends of the SOA
115
. To ensure a sufficient measurement sensitivity in the above-described evaluation of the SOA
115
, CW current driving is executed.
However, for CW current driving of the chip of the SOA
115
, the chip of the SOA
115
must be mounted on a heat sink that is excellent in heat dissipation. Since the evaluation chip must be bonded, it cannot be mounted in a product.
In addition, to evaluate the characteristic of the SOA
115
, its two ends must accurately be coupled to fibers. To do this, a fine optical fiber alignment is needed at the two ends of the SOA
115
. Furthermore, precise alignment on the submicron order is necessary. Measuring the gain by the procedure for both end facets of the SOA takes a lot of time.
Hence, in the above-described conventional evaluation method, chip evaluation is executed by sampling inspection. The characteristics of chips to be used for products are unknown.
Additionally, the SOA
115
has a broad gain bandwidth. Hence, to accurately evaluate the characteristic of the SOA
115
, the dependence of the gain on wavelength must be measured.
The SOA
115
must also be evaluated to check how much the gain characteristic changes depending on the polarized state of incident light (the dependence of the gain on polarization). The number of evaluation items is larger than that of a semiconductor laser, and therefore, the inspection is time-consuming.
SUMMARY OF THE INVENTION
The present invention has been made to solve the above problems, and has as its object to make it possible to continuously and accurately evaluate the characteristics of all manufactured semiconductor optical amplifiers (chips) in a short time with an arrangement more inexpensive and simpler than before by, e.g., executing characteristic evaluation such as characteristic screening of elements to be used for products without using any fiber coupling.
In order to achieve the above object, according to the present invention, there is provided a semiconductor optical amplifier characteristic evaluation method comprising supplying the current to a semiconductor optical amplifier, measuring an optical output generated by the semiconductor optical amplifier that has received the current, measuring transmission light obtained by transmitting the optical output through optical transmission adjustment means, and evaluating a characteristic of the semiconductor optical amplifier on the basis of a measurement result of the optical output and a measurement result of the transmission light without using an optical input to the semiconductor optical amplifier.
REFERENCES:
patent: 5917649 (1999-06-01), Mori et al.
patent: 6480318 (2002-11-01), Mori et al.
patent: 6587261 (2003-07-01), Stephens et al.
Ito Toshio
Kamioka Hiroyuki
Magari Katsuaki
Oohashi Hiromi
Suzuki Yasuhiro
Blakely & Sokoloff, Taylor & Zafman
Hellner Mark
Nippon Telegraph and Telephone Corporation
LandOfFree
Semiconductor optical amplifier characteristic evaluation... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Semiconductor optical amplifier characteristic evaluation..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Semiconductor optical amplifier characteristic evaluation... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3221379