JPH03186027A - Connection switching system for optical network - Google Patents

Abstract

PURPOSE:To miniaturize a switching part, to increase profitability and to eliminate the possibility that a signal level becomes unstable with the switching part by switching a DC bias current supplied to laser diodes through a switch and switching connections between an electronic information device and terminal devices. CONSTITUTION:The power terminals (c) or (m) DC superposing circuits N1.n-Nm.n corresponding to terminal equipment Tn are connected to the (m) fixed contacts of switch SWn, the movable contact of the switch SWn is connected to the negative electrode of a DC power source E, and the positive electrode of the power source is grounded. Then a switch SWj corresponding to a terminal Tj is changed over to connect the power source E to one of the (m) DC superposing circuits N1.j-Nm.j and the DC bias current Io is supplied to one corresponding laser diode among D1.j-Dm.j. Consequently, general small-sized, inexpensive switches for DC switching which need not have high frequency characteristics are usable and the signal level never becomes unstable owing to the loss characteristics of the switches.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" This invention relates to improvements in switching connection systems for optical networks.

“Conventional technology” Conventional high-speed optical LAN (Local Area Net
For example, as shown in FIG.
D! 0 light emitting element LD, which is supplied to and converted into an optical signal;
, LD-rich optical signals are each connected to optical fiber cable L+
,L.

The signals are supplied to the light receiving elements R, , R, and converted into electrical signals, which are then supplied to the terminal devices T, , T, respectively.

Note that the electronic information devices C, , C, are for current use, and C3 is for bank-up use. The switches SW1 and SWt respectively connect the terminal device T or T2 to one of the electronic information devices C1 to C1.

The optical LAN shown in FIG. 6 is connected to the electrical switch s shown in FIG.
Optical switches PSW+, PSWz instead of w,,sw
This is the case when using . Electronic information device C+ (i=1 to 3
) is supplied to the light emitting elements LD, , and LDt,z, converted into optical signals, and supplied to the optical switches psw and PSWX, respectively, via the optical fiber cable 2. Each optical switch is coupled directly to one end of the optical fiber cable L1 or x.

“Problems to be solved by the invention” High-speed light 1. In AN, the output signals of electronic information devices are several hundred.
Because of the high speed of megabift/second, the electrical switches sw, , sw in the optical LAN shown in Fig. 5 must be able to transmit extremely high frequencies, and for this reason, they are large and
The problem was that it was expensive.

Although the optical switch shown in FIG. 6 does not have the above-mentioned problem with high frequency characteristics, it has been difficult to obtain stable optical loss characteristics.

This invention was made against this background, and its purpose is to make the switch section in a high-speed optical LAN more compact and economical, and to prevent the possibility of the signal level becoming unstable due to the switch section. It is about improving.

One of the optical network switching connection systems of the present invention supplies signals from electronic information devices to n (an integer of 2 or more, the total number of terminal devices) laser diodes, and The output light of the laser diode is supplied to the corresponding terminal device through an optical fiber cable, and the magnitude of the DC bias current supplied to each of the laser diodes is switched, so that each laser diode can be operated in either the light emitting diode mode or the laser oscillation mode. This switches each of the laser diodes and the corresponding terminal device and the electronic information device into a disconnected state or a connected state, respectively.

Another optical network switching connection method of the present invention is to transfer the signal of the i-th (i=1.2·, mum is an integer of 2 or more) electronic information device to the n (integer of 2 or more, mum is an integer of 2 or more) electronic information device total number)
Laser diodes D,,;Dm,! ...;D1
3. to operate each of those laser diodes in light emitting diode mode, and those laser diodes D i + l ; D i
+ 1...;Dt, a (t=l, 2..., m)
are respectively coupled to the first to nth terminal devices through optical fiber cables, and the jth (j=1. 2..., n
) said laser diode D 1 coupled to a terminal device;
j; D! + j...; By selecting one of DI1 and j, increasing its DC current and switching it from the light emitting diode mode to the laser oscillation mode, the laser diode in that laser oscillation mode The above-mentioned terminal device and electronic information device corresponding to each other are switched from a non-connected state to a connected state.

"Embodiment" An embodiment of the present invention will be described with reference to FIGS. 1 and 2. The output of the electronic information device C, (m is an integer of 2 or more and represents the total number of electronic information devices) is the DC superimposition circuit N, 1 to N, (m is an integer of 2 or more and represents the total number of terminal devices). , are connected to their input terminals a. DC superimposition circuit N, 1 to N,
The output terminals of 1 and 1 are each a laser diode D1.1.
~D@+R is connected to the cathode, and its anode is grounded. Note that the first subscript m of the code indicating the laser diode indicates the number m of the electronic information device C1, and the next subscript 1.
2. ..., n indicates the number of the corresponding terminal bag WIT r to T7. (The same applies to the DC superimposing circuit Ni, j, the laser diode Di+jl, the optical fiber cable L i , J, or the light receiving element Ri + j, etc.)
Laser diodes D1.1 to D,1 are each coupled to one end of optical fiber cable L@+I to L11+ll, and the other ends of these cables are connected to light receiving elements R0,1 to Rlj.
+11, respectively, and the electrical output terminals of these light receiving elements are connected to terminal devices T, -T7, respectively.

The connection relationships related to other electronic information devices C0 to C, -1 are also the same as in the case of C, described above. In this way, the output terminals of the m light receiving elements R1, -Re, (j = 1 to n) are connected to the common terminal device TJ.

m DC superimposition circuits N to N m corresponding to the terminal device T7
, 11 are respectively connected to the m fixed contacts of the switch SW7, the movable contacts of the switches SW and 1 are connected to the negative pole of the DC power supply E, and the positive pole of the power supply is grounded. Other terminal devices T1. T z , . . . and corresponding DC superimposition circuits N3. , ~N 11+
l: N + + Z~NIL,! . . . are similarly connected to the switches SW + , S W z , . . . By switching the switch SW corresponding to the terminal device Tj (j=1 to n), the DC source E is connected to one of the m DC superimposing circuits N11, ~N 11 + J, and the corresponding laser is connected. Diode D7.4~
A DC bias current of 1° is supplied to one of D□. The high frequency signal supplied to the input terminal a of each DC superimposing circuit N i + j is passed through the DC blocking capacitor 11 and the resistor 12 in sequence, and is then connected to the laser diode D81 through the output terminal.
is supplied to DC blocking capacitor 11 and resistor 12
The connection point is connected to the power supply terminal C via the high frequency choke coil 13.

By the way, the current vs. output characteristics of the laser diode D and 1 are shown in Figure 2A, and when the current flowing through the diode is below the threshold current I, it becomes a light emitting diode mode, and the laser is in a state where only weak light is generated. The diode enters the laser oscillation mode and a strong output light corresponding to the current is obtained when the supplied current is a threshold value T. This is the case when the temperature exceeds R■. Figure 2B shows the light emitting diode D i + j
15 is a diagram showing the current waveform flowing through the switch SW, and characteristic 15 is a switch SW connected to the DC power supply and a DC bias Q.
7JtIo is supplied, and characteristic 16 is directly
This is the case when it is not connected to the IL power supply E, that is, when the DC bias current is zero.

When the laser diode D i 1 is in the light emitting diode mode, the output light is extremely weak and can be ignored in practical terms, and only the output light in the laser oscillation mode is received by the light receiving element Ri + j through the optical fiber cables L and 1. It is detected, converted into an electrical signal, and supplied to the terminal device TJ.

Note that when using the laser diode D i + j in the light emitting diode mode, a small DC bias voltage (current) may be supplied as necessary, taking into consideration the reverse withstand voltage of the diode, as shown in Fig. 3. For this purpose, the m fixed contacts of the switch SW are connected to the negative electrode of the DC 15 source e via the diode 17, and the positive electrode thereof is grounded. The terminal voltage of DC power supply e is DC'/PL power RH
This is a fairly small value compared to . The laser diode which is not connected to the DC power supply by the switch SWJ is connected to the DC power supply e via the diode 17, and a small bias current is supplied thereto.

As shown in FIG. 4, the terminal device T in FIG. 1, (j=1
% n) and the corresponding optical fiber cable L I +
The terminals of j−L @+ j are respectively connected to the input ends of optical coupler PC4, and the output ends of optical coupler PC are connected to light receiving elements R,
It is also possible to connect the output to the terminal device TJ.

In this case, the number of light-receiving elements can be reduced.As is clear from the explanation of 0 or more, in this invention, the magnitude of the DC bias current supplied to each laser diode is changed by a switch, and each laser diode is set to a light-emitting diode mode. The laser oscillation mode is switched to either one of the laser oscillation modes, and thereby each laser diode and the corresponding terminal device and electronic information device are brought into a disconnected state or a connected state, respectively.

"Effect of the Invention J According to this invention, the switching connection between the electronic information device and the terminal device is performed by switching the DC bias current supplied to the laser diode using a switch. There is no longer a need for expensive high frequency compatible switches or optical switches with unstable optical loss characteristics, and it is now possible to use general small and inexpensive switches for direct current switching that do not require high frequency characteristics. Therefore, there is no fear that the signal level will become unstable due to the loss characteristics of the switch.

[Brief explanation of drawings]

FIG. 1 is a wiring diagram showing an embodiment of the present invention, FIGS. 2A and B are supply current vs. optical output characteristics and supply current waveform diagrams of the laser diode shown in FIG. 1, respectively, and FIG. Figure 4 is a wiring diagram of the main parts when a small DC bias current is constantly flowing through the laser diode. Figure 4 shows a common light receiving system by connecting optical couplers to the terminals of the optical fiber cables corresponding to each terminal device in Figure 1. A wiring diagram of the main parts when coupled to an element, Figure 5 is a block diagram of an optical LAN using a conventional electrical switch, and Figure 6 is a diagram of an optical LAN using a conventional optical switch.
FIG.

Claims (2)

[Claims] (1) Supplying a signal from an electronic information device to n (an integer greater than or equal to 2, the total number of terminal devices) laser diodes, and supplying the output light of the laser diodes to each corresponding terminal device through an optical fiber cable, By switching the magnitude of the DC bias current supplied to each of the laser diodes, each laser diode is switched to either the light emitting diode mode or the laser oscillation mode. An optical network switching connection method that disconnects or connects information devices. (2) The signal of the i-th (i=1, 2..., m; m is an integer of 2 or more) electronic information device is transmitted to n (an integer of 2 or more, the total number of terminal devices) laser diodes D_i_,_1 ;D_i
_, _2...;D_i_, _n to operate their respective laser diodes in light emitting diode mode;
_2...;D_i_, __n (i=1, 2..., m)
are coupled to the first to nth terminal devices respectively through optical fiber cables, and the laser diodes D_1_,_ are coupled to the jth (j=1, 2..., n) terminal devices.
By selecting one of D_2_,_j...,D_n_,_j and increasing its DC bias current to switch from the light emitting diode mode to the laser oscillation mode, the laser in that laser oscillation mode An optical network switching connection method that switches between a diode and the corresponding terminal device and electronic information device from a non-connected state to a connected state.