Optical communications – Diagnostic testing – Fault detection
Reexamination Certificate
1999-05-26
2004-05-18
Pascal, Leslie (Department: 2733)
Optical communications
Diagnostic testing
Fault detection
C398S035000, C398S107000
Reexamination Certificate
active
06738578
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an optical communication method and apparatus used in a field of radio communication employing light, such as infrared light.
2. Description of the Related Art
In the field of radio communication, employing infrared light, there is prescribed the subcarrier frequency allocation by EIAJ (Electronics Industrial Association of Japan) or IEC (International Electrotechnical Commission).
There are a wide variety of equipments for radio communication with infrared light. Most well-known are a so-called remote controller for a television receiver or a video tape recorder employing infrared light and a so-called cordless headphone for receiving music signals transmitted over a radio route from an audio player with infrared light. The subcarrier frequency range used in radio communication with infrared rays in the above-mentioned remote controller is 33 to 40 kHz, while that used in the above-mentioned music signal transmission such as by the cordless headphone is 2 to 6 MHz.
A high-speed communication network, employing infrared rays, and which is made up of a sole control node (equipment)
200
and plural control nodes
260
, such as three controlled nodes
260
A to
260
C, as shown in
FIG. 1
, is envisioned, and is assumed to do time-divisionally multiplexed communication as shown in FIG.
2
.
Referring to
FIGS. 1 and 2
, a control block B
1
is used for transmitting the control information from the control node
200
to each controlled node
260
. This control block B
1
periodically receives signals. A given control block is separated from the next control block by plural timeslots SL (four time slots SL
1
to SL
4
in the example of FIG.
2
). Each node transmits the transfer blocks B
2
(transfer blocks B
2
A, B
2
B and B
2
C in the example of
FIG. 2
) within this time slot SL to transfer the data.
Referring to
FIG. 3
, a portion of the aforementioned control block B
1
is used as a use permission signal (transmission permission signal) specifying the permission of use of the time slot SL. This use permission signal is sent by the control node
200
to each controlled node
260
. In the example shown in
FIGS. 2 and 3
, the use permission signal in the control block B
1
is first checked and first the controlled node
260
A transfers the transfer block B
2
A to the control node
200
. The control node
200
then transfers the transfer block B
2
B to the totality of the controlled nodes
260
. The controlled node
260
C transfers the transfer block B
2
C to the control node
200
.
This network is in need of a broad frequency range for realization of a high-speed communication. Also, in order to assure co-existence with the above-mentioned systems, such as remote controller or cordless headphone, this network performs the communication using the subcarrier frequency not lower than 6 MHz, as shown shaded in FIG.
4
.
The internal block structure of the control node
200
and the controlled node
260
is shown in FIG.
5
.
In this figure, the control node
200
has a transmitter
210
and a receiver
220
, while the controlled node
260
also has a transmitter
240
and a receiver
250
. The transmitter
210
of the control node
200
has an orthonormal modulation circuit
211
and a light emission circuit
212
while the receiver
220
includes a light reception circuit
221
and an orthonormal demodulation circuit
222
. Similarly, the transmitter
240
of the controlled node
260
has an orthonormal modulation circuit
241
and a light emission circuit
242
, while the receiver
250
has a light reception circuit
251
and an orthonormal demodulation circuit
252
.
The orthonormal modulation circuit
211
of the control node
200
modulates a transmission signal S
201
to output a modulated signal S
202
composed of frequency components not less than 6 MHz. This modulated signal S
202
is inputted to the light emission circuit
212
, which then amplitude-modulates the infrared rays based on the modulated signal S
202
. That is, the light emission circuit
212
includes a light emitting diode LED emitting infrared rays, and drives this light emitting diode LED based on the modulated signal S
202
. This causes the light emission circuit
212
to output the infrared rays S
203
amplitude-modulated based on the modulated signal S
202
.
In the receiver
250
of the controlled node
260
, the infrared rays S
203
outputted by the control node
200
are received by the reception circuit
251
. This reception circuit
251
includes a photodiode and receives the infrared rays S
203
to convert the received rays into electrical signals. The reception circuit
251
also includes e.g., a high-pass filter which cuts the dc components of the electrical signals. An output signal S
204
of the reception circuit
251
is inputted to the orthogonal demodulation circuit
252
, which then orthogonally demodulates the signal S
204
to reproduce the same reception signal S
205
as the transmission signal S
201
.
Meanwhile, the transmitter
240
of the controlled node
260
is substantially of the same structure as the transmitter
210
of the control node
200
, while the receiver
220
of the control node
200
is substantially of the same structure as the receiver
250
of the controlled node
260
. That is, the orthogonal modulation circuit
241
of the controlled node
260
modulates the transmission signal S
211
to output a modulated signal S
212
composed of a frequency component not lower than 6 MHz. The light emission circuit
242
amplitude-modulates the infrared light based on the modulated signal S
212
. The light emission circuit
242
outputs the infrared rays S
213
amplitude-modulated based on the modulated signal S
212
. The receiver
220
of the control node
200
also receives the infrared rays S
213
from the controlled node
260
to convert the infrared rays into electrical signals while cutting off the dc components of the electrical signals. An output signal S
214
of the reception circuit
221
then is orthogonally demodulated to regenerate the same electrical signals S
215
as the transmitted signal S
211
.
FIG. 6
shows the amplitude (light emission intensity) of the infrared rays S
203
modulated on the basis of the modulated signals S
202
.
FIG. 6
shows the control block B
1
and the transfer block B
2
B transmitted by the control node
200
.
In the high-speed radio communication, employing infrared rays, as described above, the following problem arises in connection with the communication means for the high-speed radio communication, especially the above-mentioned transmitter.
Since the light emission circuit of the transmitter executes amplitude modulation, as discussed above, the infrared light of a pre-set constant level is perpetually outputted even in the absence of transmission signals, that is when no transmission is being preformed, as may be seen from FIG.
6
. That is, since the infrared rays are being outputted in a mode of transmitting a signal only once every 1000 periods, the infrared rays are radiated wastefully for 999 periods, thus increasing the power consumption.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a method and apparatus for optical communication whereby it is possible to reduce the power consumption of the light emission circuit.
In one aspect, the present invention provides an optical communication method used in a communication network in which communication is had between a control node and a plurality of controlled nodes using light rays amplitude-modulated by carrier modulation signals of a first pre-set frequency range. The communication method includes a step of transmitting a transmission permission signal from the control node to each controlled node, and a step of starting or interrupting light emission of the light rays with desired transient characteristics by each controlled node having reference to the transmission permission signal.
In another aspect, the present invention provides an optical communicati
Frommer William S.
Frommer & Lawrence & Haug LLP
Pascal Leslie
Smid Dennis M.
Sony Corporation
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