Optical access network method, optical access network, and optical switch for optical access network

• US 20060127087A1
• Filed: 11/14/2005
• Published: 06/15/2006
• Est. Priority Date: 11/12/2004
• Status: Active Grant

• Current Assignee: NEC Communication Systems Limited (NEC Corporation)
• Original Assignee: NEC Communication Systems Limited (NEC Corporation)
• Inventors: Kasai, Hiroyuki, Kobayashi, Hirokazu, Ueda, Hiromi, Nomura, Takumi, Tsuboi, Toshinori, Endo, Hiroyuki, Makino, Kunitetsu
• Granted Patent: US 7,577,362 B2
• Time in Patent Office: Days
• US Class Current: 398/45
• CPC Class Codes: H04J 14/0226 Fixed carrier allocation, e.g. according to service
• CPC Class Codes: H04J 14/0227 Operation, administration, maintenance or provisioning [OAMP] of WDM networks, e.g. media access, routing or wavelength allocation
• CPC Class Codes: H04J 14/0246 using one wavelength per ONU
• CPC Class Codes: H04J 14/0247 Sharing one wavelength for at least a group of ONUs
• CPC Class Codes: H04J 14/025 using one wavelength per ONU, e.g. for transmissions from-ONU-to-OLT or from-ONU-to-ONU
• CPC Class Codes: H04J 14/0252 Sharing one wavelength for at least a group of ONUs, e.g. for transmissions from-ONU-to-OLT or from-ONU-to-ONU
• CPC Class Codes: H04J 14/0282 WDM tree architectures
• CPC Class Codes: H04Q 11/0005 Switch and router aspects
• CPC Class Codes: H04Q 11/0067 Provisions for optical access or distribution networks, e.g. Gigabit Ethernet Passive Optical Network (GE-PON), ATM-based Passive Optical Network (A-PON), PON-Ring

Abstract

An optical access network method, an optical access network and an optical switch for an optical access network, capable of solving all the three problems in the conventional GE-PON: transmission distance problem, security problem and communication interference problem. The optical access network comprises an OLT, a plurality of ONUs and one or more stages of optical switches, which are connected one another. In the direction from the OLT to the ONU, each frame (packet) transmitted from the OLT to one of the ONUs is checked so that only the destination ONU specified in the frame (packet) is connected to the OLT. In the direction from the ONU to the OLT, a control message transmitted from the OLT to one of the ONUs is checked so that only one ONU which has been given a transmission allowance from the OLT is connected to the OLT with respect to each frame (packet).

Claims

1. An optical access network method wherein:

a center terminal, a plurality of remote terminals, and one or more optical switches are formed in a tree structure; and

the optical switch forwards a downlink signal transmitted from the center terminal to one of the remote terminals specified by the center terminal based on information from the downlink signal, and forwards an uplink signal transmitted from the remote terminal specified by the center terminal to the center terminal based on the information from the downlink signal.

3. The optical access network method claimed in claim 1, wherein at most n₁·

n₂·

n₃ . . . n_m−

₁ pieces of n_m×

1 optical switches (n_m;

an integer, 1≦

m≦

s) in the mth stage of the tree structure or the mth position from the center terminal are replaced by n_m×

1 optical splitters.

5. The optical access network method claimed in claim 1, wherein:

the tree structure consists of 1 stage or “

s”

indicating the last position of the optical switch from the center terminal is 1, and one n₁×

1 optical switch (n₁;

an integer) is provided;

the 1 side of the n₁×

1 optical switch is connected through an optical fiber to the center terminal;

the n₁ side of the n₁×

1 optical switch is connected through optical fibers to at most n₁ pieces of remote terminals; and

the n₁×

1 optical switch forwards a downlink signal transmitted from the center terminal to one remote terminal specified by the center terminal based on information from the downlink signal, and forwards an uplink signal transmitted from the remote terminal specified by the center terminal to the center terminal based on the information from the downlink signal.

7. The optical access network method claimed in claim 1, wherein:

the tree structure consists of 2 stages, or “

s”

indicating the last position of the optical switch from the center terminal is 2;

one n₁×

1 optical switch (n₁;

an integer) is provided as the first optical switch from the center terminal;

at most n₁ pieces of n₂×

1 optical switches (n₂;

an integer) are provided as the second optical switches from the center terminal;

the 1 side of the first n₁×

1 optical switch is connected through an optical fiber to the center terminal;

the n₁ side of the first n₁×

1 optical switch is connected through optical fibers to remote terminals or the 1 sides of the second n₂×

1 optical switches;

the n₂ sides of the second n₂×

1 optical switches are connected through optical fibers to at most n₁·

n₂ pieces of remote terminals; and

the n₁×

1 optical switch (i=1,

     2) forwards a downlink signal transmitted from the center terminal to one remote terminal specified by the center terminal based on information from the downlink signal, and forwards an uplink signal transmitted from the remote terminal specified by the center terminal to the center terminal based on the information from the downlink signal.

9. The optical access network method claimed in claim 1, wherein:

the tree structure consists of 2 stages, or “

s”

indicating the last position of the optical switch from the center terminal is 2;

one n₁×

1 optical splitter (n₁;

an integer) is provided in place of the first optical switch from the center terminal;

at most n₁ pieces of n₂×

1 optical switches (n₂;

an integer) are provided as the second optical switches from the center terminal;

the 1 side of the first n₁×

1 optical splitter is connected through an optical fiber to the center terminal;

the n₁ side of the first n₁×

1 optical splitter is connected through optical fibers to remote terminals or the 1 sides of the second n₂×

1 optical switches;

the n₂ sides of the second n₂×

1 optical switches are connected through optical fibers to at most n₁·

n₂ pieces of remote terminals; and

the n₂×

1 optical switch forwards a downlink signal transmitted from the center terminal to one remote terminal specified by the center terminal based on information from the downlink signal, and forwards an uplink signal transmitted from the remote terminal specified by the center terminal to the center terminal based on the information from the downlink signal.

11. The optical access network method claimed in claim 1, wherein the tree structure consists of 2 stages, or “

s”

indicating the last position of the optical switch from the center terminal is 2;

one n₁×

1 optical switch (n₁;

an integer) is provided as the first optical switch from the center terminal;

at most n₁ pieces of n₂×

1 optical splitters (n₂;

an integer) are provided in place of the second optical switches from the center terminal;

the ₁ side of the first n₁×

1 optical splitter is connected through an optical fiber to the center terminal;

the n₁ side of the first n₁×

1 optical splitter is connected through optical fibers to remote terminals or the 1 sides of the second n₂×

1 optical splitters;

the n₂ sides of the second n₂×

1 optical splitters are connected through optical fibers to at most n₁·

n₂ pieces of remote terminals; and

the n₁×

1 optical switch forwards a downlink signal transmitted from the center terminal to one remote terminal specified by the center terminal based on information from the downlink signal, and forwards an uplink signal transmitted from the remote terminal specified by the center terminal to the center terminal based on the information from the downlink signal.

16. The optical access network claimed in claim 1, wherein at most n₁·

n₂·

n₃ . . . n_m−

₁ pieces of n_m×

1 optical switches (n_m;

an integer, 1≦

m≦

s) in the mth stage of the tree structure or the mth position from the center terminal are replaced by n_m×

1 optical splitters.

2. An optical access network method comprising the steps of:

setting one n₁×

1 optical switch (n₁;

an integer) as the first optical switch from a center terminal;

setting at most n₁ pieces of n₂×

1 optical switches (n₂;

an integer) as the second optical switches from the center terminal;

setting at most n₁·

n₂ pieces of n₃×

1 optical switches (n₃;

an integer) as the third optical switches from the center terminal;

setting at most n₁·

n₂·

n₃ . . . n_k−

₁ pieces of n_k×

1 optical switches (n_k;

an integer) as the kth optical switches from the center terminal;

setting at most n₁·

n₂·

n₃ . . . n_k . . . n_s−

₁ pieces of n_s×

1 optical switches (n_s;

an integer, k≦

s) as the last optical switches from the center terminal;

connecting the center terminal to the 1 side of the first n₁×

1 optical switch through an optical fiber;

connecting the n₁ side of the first n₁×

1 optical switch to remote terminals or the 1 sides of the second n₂×

1 optical switches through optical fibers;

connecting the n₂ side of the second n₂×

1 optical switch to remote terminals or the 1 sides of the third n₃×

1 optical switches through optical fibers;

connecting the 1 side of the kth n_k×

1 optical switch to the n_k−

₁ side of the (k−

1)th n_k−

₁×

1 optical switch from the center terminal through an optical fiber;

connecting the n_k side of the kth n_k×

1 optical switch to remote terminals or the 1 sides of the (k+1)th n_k+₁×

1 optical switches from the center terminal through optical fibers;

connecting the 1 side of the sth n_s−

₁×

1 optical switch to the n_s−

₁ side of the (s−

1)th n_s−

₁×

1 optical switch from the center terminal through an optical fiber; and

connecting the n_s side of the sth n_s×

1 optical switch to remote terminals;

wherein the n_i×

1 optical switch (i=1, 2, 3, . . . , k, . . . s) forwards a downlink signal transmitted from the center terminal to one remote terminal specified by the center terminal based on information from the downlink signal, and forwards an uplink signal transmitted from the remote terminal specified by the center terminal to the center terminal based on the information from the downlink signal.

4. The optical access network method claimed in claim 2, wherein at most n₁·

n₂·

n₃ . . . n_m−

₁ pieces of n_m×

1 optical switches (n_m;

an integer, 1≦

m≦

s) in the mth stage of the tree structure or the mth position from the center terminal are replaced by n_m×

1 optical splitters.

6. The optical access network method claimed in claim 2, wherein:

the tree structure consists of 1 stage or “

s”

indicating the last position of the optical switch from the center terminal is 1, and one n₁×

1 optical switch (n₁;

an integer) is provided;

the 1 side of the n₁×

1 optical switch is connected through an optical fiber to the center terminal;

the n₁ side of the n₁×

1 optical switch is connected through optical fibers to at most n₁ pieces of remote terminals; and

the n₁×

1 optical switch forwards a downlink signal transmitted from the center terminal to one remote terminal specified by the center terminal based on information from the downlink signal, and forwards an uplink signal transmitted from the remote terminal specified by the center terminal to the center terminal based on the information from the downlink signal.

8. The optical access network method claimed in claim 2, wherein:

the tree structure consists of 2 stages, or “

s”

indicating the last position of the optical switch from the center terminal is 2;

one n₁×

1 optical switch (n₁;

an integer) is provided as the first optical switch from the center terminal;

at most n₁ pieces of n₂×

1 optical switches (n₂;

an integer) are provided as the second optical switches from the center terminal;

the 1 side of the first n₁×

1 optical switch is connected through an optical fiber to the center terminal;

the n₁ side of the first n₁×

1 optical switch is connected through optical fibers to remote terminals or the 1 sides of the second n₂×

1 optical switches;

the n₂ sides of the second n₂×

1 optical switches are connected through optical fibers to at most n₁·

n₂ pieces of remote terminals; and

the n₁×

1 optical switch (i=1,

     2) forwards a downlink signal transmitted from the center terminal to one remote terminal specified by the center terminal based on information from the downlink signal, and forwards an uplink signal transmitted from the remote terminal specified by the center terminal to the center terminal based on the information from the downlink signal.

10. The optical access network method claimed in claim 2, wherein:

the tree structure consists of 2 stages, or “

s”

indicating the last position of the optical switch from the center terminal is 2;

one n₁×

1 optical splitter (n₁;

an integer) is provided in place of the first optical switch from the center terminal;

at most n₁ pieces of n₂×

1 optical switches (n₂;

an integer) are provided as the second optical switches from the center terminal;

the 1 side of the first n₁×

1 optical splitter is connected through an optical fiber to the center terminal;

the n₁ side of the first n₁×

1 optical splitter is connected through optical fibers to remote terminals or the 1 sides of the second n₂×

1 optical switches;

the n₂ sides of the second n₂×

1 optical switches are connected through optical fibers to at most n₁·

n₂ pieces of remote terminals; and

the n₂×

1 optical switch forwards a downlink signal transmitted from the center terminal to one remote terminal specified by the center terminal based on information from the downlink signal, and forwards an uplink signal transmitted from the remote terminal specified by the center terminal to the center terminal based on the information from the downlink signal.

12. The optical access network method claimed in claim 2, wherein the tree structure consists of 2 stages, or “

s”

indicating the last position of the optical switch from the center terminal is 2;

one n₁×

1 optical switch (n₁;

an integer) is provided as the first optical switch from the center terminal;

at most n₁ pieces of n₂×

1 optical splitters (n₂;

an integer) are provided in place of the second optical switches from the center terminal;

the 1 side of the first n₁×

1 optical splitter is connected through an optical fiber to the center terminal;

the n₁ side of the first n₁×

1 optical splitter is connected through optical fibers to remote terminals or the 1 sides of the second n₂×

1 optical splitters;

the n₂ sides of the second n₂×

1 optical splitters are connected through optical fibers to at most n₁·

n₂ pieces of remote terminals; and

the n₁×

1 optical switch forwards a downlink signal transmitted from the center terminal to one remote terminal specified by the center terminal based on information from the downlink signal, and forwards an uplink signal transmitted from the remote terminal specified by the center terminal to the center terminal based on the information from the downlink signal.

13. The optical access network method claimed in claim 2, wherein the information obtained from the downlink signal is a logical link identifier and frame length specified in a frame defined by IEEE 802. 3ah transmitted from the center terminal to the specific one of the plurality of remote terminals.

17. The optical access network claimed in claim 2, wherein at most n₁·

n₂·

n₃ . . . n_m−

₁ pieces of n_m×

1 optical switches (n_m;

an integer, 1≦

m≦

s) in the mth stage of the tree structure or the mth position from the center terminal are replaced by n_m×

1 optical splitters.

14. An optical access network comprising a center terminal, a plurality of remote terminals, and one or more optical switches, which are formed in a tree structure, wherein the optical switch forwards a downlink signal transmitted from the center terminal to one of the remote terminals specified by the center terminal based on information from the downlink signal, and forwards an uplink signal transmitted from the remote terminal specified by the center terminal to the center terminal based on the information from the downlink signal.

15. An optical access network comprising:

one n₁×

1 optical switch (n₁;

an integer) as the first optical switch from a center terminal;

at most n₁ pieces of n₂×

1 optical switches (n₂;

an integer) as the second optical switches from the center terminal;

at most n₁·

n₂ pieces of n₃×

1 optical switches (n₃;

an integer) as the third optical switches from the center terminal;

at most n₁·

n₂·

n₃ . . . n_k−

₁ pieces of n_k×

1 optical switches (n_k;

an integer) as the kth optical switches from the center terminal;

at most n₁·

n₂·

n₃ . . . n_k . . . n_s−

₁ pieces of n_s×

1 optical switches (n_s;

an integer, k≦

s) as the last optical switches from the center terminal;

wherein;

the center terminal is connected through an optical fiber to the 1 side of the first n₁×

1 optical switch;

the n₁ side of the first n₁×

1 optical switch is connected through optical fibers to remote terminals or the 1 sides of the second n₂×

1 optical switches;

the n₂ side of the second n₂×

1 optical switch is connected through optical fibers to remote terminals or the 1 sides of the third n₃×

1 optical switches;

the 1 side of the kth n_k×

1 optical switch is connected through an optical fiber to the n_k−

₁ side of the (k−

1)th n_k−

₁×

1 optical switch from the center terminal;

the n_k side of the kth n_k×

1 optical switch is connected through optical fibers to remote terminals or the 1 sides of the (k+1)th n_k+₁×

1 optical switches from the center terminal;

the 1 side of the sth n_s×

1 optical switch is connected through an optical fiber to the n_s×

1 side of the (s−

1)th n_s−

₁×

1 optical switch from the center terminal;

the n_s side of the sth n_s×

1 optical switch is connected to remote terminals; and

the n₁×

1 optical switch (i=1, 2, 3, . . . , k, . . . s) forwards a downlink signal transmitted from the center terminal to one remote terminal specified by the center terminal based on information from the downlink signal, and forwards an uplink signal transmitted from the remote terminal specified by the center terminal to the center terminal based on the information from the downlink signal.

18. An optical switch for an optical access network comprising, at least:

a received frame analyzer for analyzing a downlink signal from a center terminal;

an uplink optical switch device; and

a downlink optical switch device;

wherein based on the analysis result obtained by the received frame analyzer, the uplink and downlink optical switch devices perform switching per packet.

19. The optical switch for an optical access network claimed in claim 18, wherein the downlink signal from the center terminal is split into two optical signals by a 2×

1 optical splitter, one of which is converted to an electrical signal to be input to the received frame analyzer, and the other is given a prescribed delay by a delay circuit to be input to the downlink optical switch device.

20. The optical switch for an optical access network claimed in claim 18, wherein:

the downlink signal transmitted from the center terminal and analyzed by the received frame analyzer is a signal of a frame format defined by IEEE 802. 3ah;

the downlink optical switch device performs switching based on a logical link identifier and frame length specified in the frame; and

the uplink optical switch device performs switching based on a control message from the center terminal.