1. An optical node system for transferring optical signals having a plurality of wavelengths in an optical ring network, said node comprising:
an optical multiplexer configured to receive said optical signals having a plurality of wavelengths, said optical multiplexer further configured to output optical signals having certain wavelengths for transmission onto said optical ring network and to route at least one optical signal having a particular wavelength to an optical transceiver; and
said optical transceiver coupled to said optical multiplexer and configured to receive said at least one incoming optical signal of said particular wavelength and to output an outgoing optical signal of said particular wavelength with light from said incoming optical signal.
2. The optical node of claim 1 wherein said optical transceiver modulates outgoing information onto at least a portion of the light of said incoming optical signal.
3. The optical node of claim 1 wherein said optical multiplexer includes a first wavelength selection device coupled to a second wavelength selection device and is configured to receive said optical signals having certain wavelengths and said outgoing optical signal and to combine said optical signals having certain wavelengths and said outgoing optical signal from said optical transceiver onto an optical output path.
4. The optical node of claim 3 wherein said first and second wavelength selection devices are on the same physical device.
5. The optical node of claim 1 wherein said optical transceiver includes:
signal conditioning circuitry configured to receive an incoming optical signal which has been modulated with incoming information to be dropped and to suppress said incoming information of said incoming optical signal in said outgoing optical signal.
6. The optical node of claim 5 wherein said optical transceiver is configured to modulate said incoming optical signal having incoming information suppressed by said signal conditioning circuitry with outgoing information.
7. The optical node of claim 5 wherein said signal conditioning circuitry substantially removes a modulated portion of said incoming optical signal modulated with incoming information to be dropped.
8. The optical node of claim 5 wherein said signal conditioning circuitry comprises at least one optical amplifier.
9. The optical node of claim 8 wherein said at least one optical signal amplifier operates in saturation.
10. A method of transferring optical signals having a plurality of wavelengths in an optical ring network, said method comprising the steps of:
receiving optical signals having a plurality of wavelengths;
outputting optical signals having certain wavelengths for transfer onto said optical ring network for transfer onto said optical ring network;
routing at least one incoming optical signal having a particular wavelength to an optical transceiver; and
outputting by said optical transceiver an outgoing optical signal of said particular wavelength using light from ad incoming optical signal.
11. The method of claim 10 further including the step of:
modulating outgoing information onto at least a portion of the light of said incoming optical signal.
12. The method of claim 11 further including the steps of:
receiving said incoming optical signal which has been modulated with incoming information; and
suppressing said incoming information of said incoming optical signal.
13. The method of claim 12 further wherein said step of modulating includes:
modulating said incoming optical signal having incoming information suppressed by said signal conditioning circuitry with outgoing information.
14. The method of claim 10 further including the step of:
combining said optical signals having certain wavelengths and said outgoing optical signal from said optical transceiver onto an optical output path.
15. The method of claim 12 wherein said step of suppressing further includes:
substantially removing said incoming information from said incoming optical signal which has been modulated with said incoming information.
16. The method of claim 12 wherein said step of suppressing includes the step of:
using at least one optical amplifier.
17. The method of claim 16 wherein said step of using includes:
operating said at least one amplifier in saturation.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A printing apparatus, comprising:
a sheet-feeding system;
a sheet-transporting system, comprising a sheet-circulating path and transporting mechanism, for receiving a recording medium from the sheet-feeding system and transporting the recording medium through an image forming system, wherein the transporting mechanism moves the recording medium along the sheet-circulating path;
said image forming system, in the sheet-circulating path, forming an image on the recording medium;
a sheet-controlling device, disposed between the sheet-feeding system and the sheet-transporting system, the sheet-controlling device controlling an entry of a sheet into the sheet-transporting system;
a sheet-detection device, disposed between the sheet-feeding system and the sheet-transporting system;
a first driving system for driving the sheet-controlling device;
a second driving system for driving the transporting mechanism; and
a controller, which upon receiving an error signal from the sheet-detection device signals the sheet-controlling device to inhibit the entry of the sheet into the sheet-transporting system and signals the transporting mechanism to continue its operation.
2. A printing apparatus of claims 1, wherein the sheet-detection device is disposed at a position upstream of the sheet-controlling device in a sheet conveyance direction.
3. A printing apparatus of claims 1, wherein the sheet-detection device is disposed at a position downstream of the sheet-controlling device in a sheet conveyance direction.
4. A printing apparatus of claims 1, wherein upon receiving the error signal from the sheet-detection device the controller discontinues operation of the sheet-controlling device.
5. A printing apparatus of claims 4, wherein the sheet-controlling device comprises an entrance roller pair.
6. A printing apparatus of claims 1, wherein the transporting mechanism moves the first sheet through the image forming system twice along the sheet-circulating path.
7. A printing apparatus of claims 1, wherein the sheet-detection device comprises a thickness sensing unit.
8. A duplex printing method performed by a printing apparatus, the method comprising:
feeding in a first sheet;
transporting the first sheet along a sheet-circulating path;
forming an image on a front side of the first sheet;
feeding in a second sheet;
detecting a sheet-feeding error;
inhibiting an entry of the second sheet into the sheet-circulating path;
forming an image on a back side of the first sheet; and
ejecting the first sheet.
9. A duplex printing method of claim 8, wherein the step of inhibiting the entry of the second sheet into the sheet-circulating path comprises:
discontinuing rotation of an entrance roller pair when the second sheet reaches the entrance roller pair.
10. A duplex printing method performed by a printing apparatus, the method comprising:
feeding in a first sheet;
transporting the first sheet along a sheet-circulating path;
forming an image on a front side of the first sheet;
feeding in a second sheet;
transporting the second sheet along the sheet-circulating path;
forming an image on a front side of the second sheet;
feeding in a third sheet;
detecting a sheet-feeding error;
inhibiting an entry of the third sheet into the sheet-circulating path;
forming an image on a back side of the first sheet;
forming an image on a back side of the second sheet; and
ejecting the first sheet and the second sheet.
11. A duplex printing method of claim 10, wherein the step of inhibiting the entry of the third sheet into the sheet-circulating path comprises:
discontinuing rotation of an entrance roller pair when the third sheet reaches the entrance roller pair.