Optical communications – Transmitter and receiver system – Including alignment between transmitter and receiver
Reexamination Certificate
2001-01-22
2004-06-15
Chan, Jason (Department: 2633)
Optical communications
Transmitter and receiver system
Including alignment between transmitter and receiver
C398S088000, C398S122000, C398S131000, C398S201000, C398S207000, C398S128000
Reexamination Certificate
active
06751422
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a spatial light communication equipment for spatially transmitting optical signals and more particularly to the spatial light communication equipment which can be used suitably for ultra-long-distance spatial optical communications such as intersatellite optical communications.
The present application claims priority of Japanese Patent Application No.2000-011338 filed on Jan. 20, 2000, which is hereby incorporated by reference.
2. Description of the Related Art
An information transmitting system using optical signals includes, in addition to a wired transmission system through an optical fiber being featured by non-inductive, low-loss and wide-band optical transmission, a spatial transmitting system using spatial light such as infrared rays. The spatial transmitting system, though it is of lower quality of transmission than the wired transmission system, can provide low-cost and highly practical communication simply by installing a spatial light communication equipment enabling communication by spatial light on transmitting side and receiving side within an unobstructed spatial range. The spatial transmission system is very advantageous in ultra-long-distance communication which costs much to install wired transmission lines such as optical fibers and/or in intersatellite optical communications in which installation of wired transmission lines is impossible, in particular.
To carry out communications using spatial light, the spatial light communication equipment installed on a transmitting side is placed opposite to one installed on a receiving side and a spatial light receiving communication equipment (hereinafter may be referred to as a receiver) receives spatial light emitted by a spatial light transmitting communication equipment (hereinafter may be referred to as a transmitter). In the case of intersatellite optical communications being ultra-long-distance communication, since the spatial light to be emitted is a light beam having directivity as sharp as about 10&mgr; rad, seizure/tracking capability and beam directivity with accuracy of about 1 &mgr;rad are required to receive the emitted beams of light.
FIG. 8
is a schematic block diagram for showing configurations of a conventional spatial light communication equipment. In this spatial light communication equipment, communications are carried out by using transmitting and receiving beams which are transmitted or received on a same optical axis between the transmitter and the receiver. A beam emitted from the transmitter (not shown) is received by an optical antenna
10
of the receiver. The beam received by the optical antenna
10
is transmitted to a beam deflector
11
. The beam deflector
11
totally reflects only the beam received through the optical antenna
10
and guides it toward a beam splitter
12
. On an optical axis of the beam totally reflected by the beam deflector
11
are placed the beam splitter
12
, a beam splitter
13
and an angle detector
14
. The beam splitter
12
allows the beam totally reflected by the beam deflector
11
to pass through itself. The beam splitter
13
allows the beam transmitted through the beam splitter
12
to pass through itself and then outputs the beam to the angle detector
14
and, at a same time, guides the beam toward an optical receiver
15
. The angle detector
14
detects an angle of deviation, relative to an optical axis of the beam totally reflected by the beam deflector
11
, of the beam transmitted through the beam splitter
13
. The optical receiver
15
converts the beam guided by the beam splitter
13
to an electrical signal and performs predetermined signal receiving processing.
On the other hand, since direction in which the optical antenna
10
is directed to the spatial light communication equipment (not shown) installed on the opposite side is displaced by an angle of deviation detected by the angle detector
14
, a transmitting signal to be transmitted to the receiver is emitted with the angle of deviation being corrected. At this point, transmitting signal to be transmitted by an optical transmitter
16
is converted to an transmitting beam as an optical signal and is output to the beam splitter
12
. The beam splitter
12
guides the transmitting beam fed by the optical transmitter
16
toward the beam deflector
11
. The beam deflector
11
, by using a control section (not shown), is adapted to improve signal receiving sensitivity of the optical receiver
15
. The beam deflector
11
also controls a deflected angle depending on angle of deviation detected by the angle detector
14
so that a direction of the transmitting beam fed by the optical antenna
10
directed to the receiver is corrected by the angle of deviation. The beam deflector
11
totally reflects the beam fed from the beam splitter
12
and guides it toward the optical antenna
10
. The optical antenna
10
transmits the beam from the beam deflector
11
to the receiver.
Thus, in the spatial light communication equipment by which communication is carried out by transmitting and receiving the beam on the same optical axis between the transmitter and receiver, by controlling an angle of the beam deflected by the beam deflector
11
, the corrected angle detected at a time of tracking the receiving beam is applied to adjustment of directions of the transmitting beam. This enables sharp directivity of beam light in the spatial light communication equipment to be implemented, with simplified configurations.
FIG. 9
is a schematic block diagram showing configurations of a conventional spatial light communication equipment in which communication is carried out using signal transmitting and receiving beams being transmitted on different optical axes. The spatial light communication equipment of this type is provided with one optical antenna for transmitting beams and another optical antenna for receiving beams to carry out communication using beams to be transmitted and received on the different optical axes between the transmitter and receiver. Therefore, a receiving beam transmitted from the transmitter is received by a signal receiving optical antenna
20
. The receiving beam received by the signal receiving optical antenna
20
is output to a beam deflector
21
. The beam deflector
21
totally reflects only the receiving beam fed from the signal receiving optical antenna
20
and guides them toward a beam splitter
22
. On an optical axis of the receiving beam totally reflected by the beam deflector
21
are placed the beam splitter
22
and an angle detector
23
. The beam splitter
22
allows the receiving beam totally reflected by the beam deflector
21
to pass through itself to output to the angle detector
23
and, at a same time, guides the beam toward an optical receiver
24
. The angle detector
23
detects an angle of deviation, relative to an optical axis of the beam totally reflected by the beam deflector
21
, of the beam transmitted through the beam splitter
22
. The optical receiver
24
converts the beam guided by the beam splitter
22
to an electrical signal and performs predetermined signal receiving processing The spatial light communication equipment shown in
FIG. 9
is provided with a control section (not shown) adapted to change the angle deflected by the beam deflector
21
depending on the angle of deviation of the transmitted light beam detected by the angle detector
23
in order to improve signal receiving sensitivity of the optical receiver
24
. An amount of the corrected angle changed by the control section is monitored by an angle transferring circuit
25
and is transferred, with high accuracy, to a beam deflector
26
.
A transmitting signal to be transmitted from the spatial light communication equipment is converted to an optical signal by an optical transmitter
27
and is output to the beam deflector
26
. The beam deflector
26
totally reflects only specified beam component in the transmitting beams and guides them to a mirror
28
. The mirror
28
guides the
Chan Alex
Chan Jason
Dickstein Shapiro Morin & Oshinsky LLP.
NEC Toshiba Space Systems, Ltd.
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