Method and system for scheduling cascaded PON

1. An apparatus for coupling between a trunk passive optical network (PON) and a leaf PON, comprising:

a trunk-side optical transceiver coupled to the trunk PON;

a leaf-side optical transceiver coupled to the leaf PON; and

an integrated circuit chip that includes an optical network unit (ONU) media access control (MAC) module, an optical line terminal (OLT) MAC module, and an on-chip memory;

wherein the OLT MAC module is configured to:

receive, from multiple logical links in the leaf PON, bandwidth-requesting frames;

generate multiple bandwidth assignments corresponding to the bandwidth-requesting frames; and

store the multiple bandwidth assignments into a bandwidth-assigning queue; and

wherein the ONU MAC module is configured to:

access the bandwidth-assigning queue;

generate a single bandwidth-requesting frame based on the multiple bandwidth-assignments; and

send the single bandwidth-requesting frame to the trunk PON.

2. The apparatus of claim 1 , wherein the trunk-side optical transceiver includes one of:

a small form-factor pluggable (SFP) transceiver;

an enhanced small form-factor pluggable (SFP+) transceiver; and

a 10 Gigabit small form-factor pluggable (XFP) transceiver.

3. The apparatus of claim 1 , wherein the integrated circuit chip and the leaf-side optical transceiver is packaged together to form an integrated module, and wherein the integrated module has a standard form factor that is in compliance with one of:

a small form-factor pluggable (SFP) specification;

an enhanced small form-factor pluggable (SFP+) specification; and

a 10 Gigabit small form-factor pluggable (XFP) specification.

4. The apparatus of claim 1 , wherein the trunk PON and the leaf PON are running at different data rates.

5. The apparatus of claim 1 ,

wherein the ONU MAC module is configured to:

receive, from the trunk PON, a bandwidth-assigning frame dedicated to a single logical link in the leaf PON, wherein the band-width assigning frame includes parameters relative to the trunk PON; and

send the bandwidth-assigning frame to the OLT MAC module; and

wherein the OLT MAC module is configured to:

receive the bandwidth-assigning frame from the ONU MAC module;

generate a new bandwidth-assigning frame by replacing the parameters relative to the trunk PON with parameters relative to the leaf PON; and

send the new bandwidth-assigning frame to the single logical link.

6. The apparatus of claim 5 , wherein the OLT MAC module is further configured to:

receive a bandwidth-requesting frame comprising parameters relative to the leaf PON; and

convert the bandwidth-requesting frame to a new bandwidth-requesting frame comprising parameters relative to the trunk PON.

7. The apparatus of claim 5 ,

wherein the OLT MAC module is further configured to:

receive a data burst in response to the new bandwidth-assigning frame; and

store the received data burst in an upstream data queue; and

wherein the ONU MAC module is configured to:

in response to determining that a bandwidth assignment included in the bandwidth-assigning frame being valid based on the parameters relative to the trunk PON, send the data burst stored in the upstream data queue upstream to the trunk PON.

8. The apparatus of claim 1 ,

wherein the ONU MAC module is configured to:

receive, from the trunk PON, a bandwidth-assigning frame assigning bandwidth to multiple logical links in the leaf PON;

extract a bandwidth assignment from the received bandwidth-assigning frame; and

send the extracted bandwidth assignment to the OLT MAC module; and

wherein the OLT MAC module is configured to:

receive the extracted bandwidth assignment;

divide the received bandwidth assignment into multiple new bandwidth assignments;

generate multiple new bandwidth-assigning frames using the multiple new bandwidth assignments; and

send the multiple new bandwidth-assigning frames to the multiple logical links.

9. The apparatus of claim 1 , wherein the ONU MAC module is further configured to:

receive a single bandwidth-assigning frame in response to the bandwidth-requesting frame;

extract a bandwidth assignment from the bandwidth-assigning frame; and

generate multiple bandwidth-assigning frames based on the extracted bandwidth assignment and information included in the bandwidth-assigning queue.

10. The apparatus of claim 1 , wherein the OLT MAC module is configured to:

receive data bursts from the multiple logical links;

store the received data bursts into a single upstream queue;

monitor status of the single upstream queue; and

in response to the single upstream queue being full, suspend generation of new bandwidth assignments.

11. The apparatus of claim 10 , wherein the ONU MAC module is further configured to remove the multiple bandwidth-assignments from the bandwidth-assigning queue after sending the single bandwidth-requesting frame to the trunk PON, thereby allowing new bandwidth assignments to be generated and stored in the bandwidth-assigning queue.

12. A cascaded passive optical network (PON), comprising:

a trunk PON;

one or more leaf PONs; and

one or more bridges coupling the trunk PON to the one or more leaf PONs, wherein a respective bridge comprises:

a trunk-side optical transceiver coupled to the trunk PON;

a leaf-side optical transceiver coupled to a leaf PON; and

an integrated circuit chip that includes an optical network unit (ONU) media access control (MAC) module, an optical line terminal (OLT) MAC module, and an on-chip memory;

wherein the OLT MAC module is configured to:

receive, from multiple logical links in the leaf PON, bandwidth-requesting frames;

generate multiple bandwidth assignments corresponding to the bandwidth-requesting frames; and

store the multiple bandwidth assignments into a bandwidth-assigning queue; and

wherein the ONU MAC module is configured to:

access the bandwidth-assigning queue;

generate a single bandwidth-requesting frame based on the multiple bandwidth-assignments; and

send the single bandwidth-requesting frame to the trunk PON.

13. The cascaded PON of claim 12 , wherein the trunk-side optical transceiver includes one of:

a small form-factor pluggable (SFP) transceiver;

an enhanced small form-factor pluggable (SFP+) transceiver; and

a 10 Gigabit small form-factor pluggable (XFP) transceiver.

14. The cascaded PON of claim 12 , wherein the integrated circuit chip and the leaf-side optical transceiver is packaged together to form an integrated module, and wherein the integrated module has a standard form factor that is in compliance with one of:

a small form-factor pluggable (SFP) specification;

an enhanced small form-factor pluggable (SFP+) specification; and

a 10 Gigabit small form-factor pluggable (XFP) specification.

15. The cascaded PON of claim 12 , wherein the trunk PON and the leaf PON are running at different data rates.

16. The cascaded PON of claim 12 ,

wherein the ONU MAC module is configured to:

receive, from the trunk PON, a bandwidth-assigning frame dedicated to a single logical link in the leaf PON, wherein the band-width assigning frame includes parameters relative to the trunk PON; and

send the bandwidth-assigning frame to the OLT MAC module; and

wherein the OLT MAC module is configured to:

receive the bandwidth-assigning frame from the ONU MAC module;

generate a new bandwidth-assigning frame by replacing the parameters relative to the trunk PON with parameters relative to the leaf PON; and

send the new bandwidth-assigning frame to the single logical link.

17. The cascaded PON of claim 16 , wherein the OLT MAC module is further configured to:

receive a bandwidth-requesting frame comprising parameters relative to the leaf PON; and

convert the bandwidth-requesting frame to a new bandwidth-requesting frame comprising parameters relative to the trunk PON.

18. The cascaded PON of claim 16 ,

wherein the OLT MAC module is further configured to:

receive a data burst in response to the new bandwidth-assigning frame; and

store the received data burst in an upstream data queue; and

wherein the ONU MAC module is configured to:

in response to determining that a bandwidth assignment included in the bandwidth-assigning frame being valid based on the parameters relative to the trunk PON, send the data burst stored in the upstream data queue upstream to the trunk PON.

19. The cascaded PON of claim 12 ,

wherein the ONU MAC module is configured to:

receive, from the trunk PON, a bandwidth-assigning frame assigning bandwidth across multiple logical links in the leaf PON;

extract a bandwidth assignment from the received bandwidth-assigning frame; and

send the extracted bandwidth assignment to the OLT MAC module; and

wherein the OLT MAC module is configured to:

receive the extracted bandwidth assignment;

divide the received bandwidth assignment into multiple new bandwidth assignments;

generate multiple new bandwidth-assigning frames using the multiple new bandwidth assignments; and

send the multiple new bandwidth-assigning frames to the multiple logical links.

20. The cascaded PON of claim 12 , wherein the ONU MAC module is further configured to:

receive a single bandwidth-assigning frame in response to the bandwidth-requesting frame;

extract a bandwidth assignment from the bandwidth-assigning frame; and

generate multiple bandwidth-assigning frames based on the extracted bandwidth assignment and information included in the bandwidth-assigning queue.

21. The cascaded PON of claim 12 , wherein the OLT MAC module is configured to:

receive data bursts from the multiple logical links;

store the received data bursts into a single upstream queue;

monitor status of the single upstream queue; and

in response to the single upstream queue being full, suspend generation of new bandwidth assignments.

22. The cascaded PON of claim 21 , wherein the ONU MAC module is further configured to remove the multiple bandwidth-assignments from the bandwidth-assigning queue after sending the single bandwidth-requesting frame to the trunk PON, thereby allowing new bandwidth assignments to be generated and stored in the bandwidth-assigning queue.

23. A method for scheduling upstream transmission in a cascaded passive optical network (PON) comprising a trunk PON and one or more leaf PONs, the method comprising:

receiving, by a bridge device coupling between the trunk PON and a leaf PON, a plurality of bandwidth-requesting frames from a plurality of logical links within the leaf PON;

generating a plurality of bandwidth assignments based on the received bandwidth-requesting frames;

storing the bandwidth assignments in a bandwidth-assigning queue;

assembling a single bandwidth-requesting frame based on the bandwidth assignments;

sending the single bandwidth-requesting frame upstream to an optical line terminal (OLT) in the trunk PON;

receiving, from the OLT in the trunk PON, a single bandwidth-assigning frame in response to the single bandwidth-requesting frame;

generating a plurality of new bandwidth-assigning frames based on the received single bandwidth-assigning frame and the bandwidth assignments stored in the bandwidth-assigning queue; and

sending the new bandwidth-assigning frames downstream to the logical links within the leaf PON.