Optical communication apparatus

Details Optical communication apparatus Optical communication apparatus

1999-06-01

2002-11-12

Pascal, Leslie (Department: 2633)

Optical: systems and elements

Deflection using a moving element

Using a periodically moving element

C359S199200, C359S199200, C359S199200, C359S199200, C370S241000, C455S069000

Reexamination Certificate

active

06480308

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical communication apparatus.
2. Description of the Related Art
FIG. 8
is a block diagram for explaining an example of the constitution of a conventional optical communication apparatus. There is a diode (hereinafter, abbreviated as LD)
1
which converts an electric signal into laser beam having a corresponding intensity and transmits the laser beam to outside via an optical fiber, not illustrated. An LD driving unit
2
drives LD
1
in accordance with transmission data (Tx. Data) inputted via a signal line
3
and an output signal
7
from APC (Auto Power Control)
5
. A portion of the laser beam emitted from LD
1
is incident on a photodiode
4
and the photodiode
4
converts the incident laser beam into an electric signal.
APC
5
controls the LD driving unit
2
in accordance with the electric signal outputted from the photodiode
4
and a reference amplitude (Tx. Ref) of a transmission signal inputted from a signal line
6
such that the intensity of the laser beam emitted from LD
1
becomes a predetermined amplitude. Laser beam transmitted via an optical fiber, not illustrated, is incident on a photodiode
8
and the photodiode
8
converts the laser beam into a corresponding electric signal. An amplifying unit
9
amplifies the electric signal outputted from the photodiode
8
by a predetermined gain and outputs the electric signal to an inner portion of the optical communication apparatus as reception data (Rx. Data) via a signal line
10
.
The transmission data is supplied to the LD driving unit
2
via the signal line
3
. The LD driving unit
2
drives LD
1
to emit laser beam in accordance with the transmission data and the output signal
7
from APC
5
. The laser beam emitted from LD
1
is transmitted to other party of communication, not illustrated, via an optical fiber, not illustrated.
The portion of the laser beam emitted from LD
1
is incident on the photodiode
4
and accordingly, an electric signal in correspondence with the intensity of the laser beam emitted from LD
1
is inputted to APC
5
. APC
5
compares the electric signal outputted from the photodiode
4
with the reference amplitude (Tx. Ref) of the transmission signal inputted from the signal line
6
and controls the LD driving unit
2
such that both maintain a predetermined relationship (for example, such that both are equal to each other). As a result, the intensity of the laser beam emitted from LD
1
always becomes a predetermined amplitude.
Further, the laser beam transmitted via an optical fiber, not illustrated, is photoelectrically converted into the corresponding electric signal by the photodiode
8
, amplified by the amplifying unit
9
by a predetermined gain and thereafter is outputted to the inner portion of the optical communication apparatus as reception data via the signal line
10
.
According to the above-described conventional optical communication apparatus, the intensity of the transmitted laser beam is always set to be a predetermined amplitude. It is general that the intensity of the laser beam is set with transmission loss of a longest optical fiber as a reference in a system thereof (a system constituted by connecting optical communication apparatus to each other).
When a power value of laser beam is set to an intensity capable of sufficiently dealing with transmission loss in an optical fiber having a longest length in a system, the system can ensure a sufficient intensity (power value).
It is said that the life of a laser diode (LD) is inversely proportional to the second through the third power of an intensity of emitted laser beam. Therefore, in the case in which an intensity of laser beam which can communicate through an optical fiber having a longest length which is predicted in using the optical fiber in a system when communication is carried out by an optical fiber having a short length, the intensity becomes excessively heavy and the life of LD is significantly shortened.
That is, in the case in which the intensity of laser beam which can communicate through the optical fiber having the long length which is predicted in using the optical fiber in a system, when lengths of optical fibers used differ from each other significantly, the intensity of laser beam inputted to a reception unit of an optical communication apparatus similarly differs significantly. For example, in the case of LAN (Local Area Network) or the like, the length of an optical fiber used is varied significantly substantially from 1 m through 2 km and accordingly, a difference in transmission losses becomes about 16 dB and the intensity of laser beam is varied significantly in accordance therewith. Such a difference is particularly significant in POF (Plastic Optical Fiber) having large transmission loss.
When the intensity of inputted laser beam differs significantly in this manner, in order to ensure an error rate at a constant value or lower in respect of input of laser beam in any intensity, the dynamic range of light in an optical communication apparatus needs to provide sufficiently widely, as a result, there poses a problem in which design of the apparatus becomes complicated and fabrication cost of the apparatus is increased.
Further, when the problem of Eye Safe is considered, it is preferable to set the intensity of laser beam as small as possible. When the intensity of laser beam is set low, in a system having significant loss (for example, a system connected by POF or the like), there poses also a problem in which the design becomes difficult owing to the problem of the dynamic range as mentioned above.
A conventional optical communication apparatus is not constituted such that control of light emitting power and reception sensitivity is dynamically carried out in accordance with a kind, a length, a situation of laying thereof, a condition of using thereof or the like of an optical fiber used. Therefore, the optical communication apparatus including the optical fiber needs to fabricate under a severe specification conscious of the worst condition, as a result, the apparatus becomes expensive. This is significant particularly in the case of using an optical transmission medium having comparatively large transmission loss such as an optical fiber made of plastic.
Therefore, the present invention relates to an optical communication apparatus resolving the above-described problem and capable of firmly executing optical communication using an optical transmission medium among optical communication apparatus under an optimum condition.
SUMMARY OF THE INVENTION
Hence, according to a first aspect of the present invention, there is provided an optical communication apparatus connected to an optical communication apparatus on other party side via an optical transmission medium for communicating a data signal with the optical communication apparatus on the other party side, the optical communication apparatus comprising drive signal outputting means for controlling a signal level of an input signal in accordance with a light emitting power control signal and outputting the input signal the signal level of which has been controlled as a drive signal, a light emitting element for emitting light at an intensity in accordance with the signal level of the drive signal and transmitting an optical signal via the optical transmission medium, test signal generating means for forming a test signal having a specific signal pattern, selecting means for selectively outputting either of the test signal and the data signal to the drive signal forming means as the input signal, a light receiving element for receiving the optical signal via the optical transmission medium and converting the received optical signal into an electric signal, detecting means for detecting whether the electric signal outputted from the light receiving element coincides with the specific signal pattern when the selecting means selects the test signal and controlling means for controlling a parameter of the light emitting power con

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