Method of and device for the fine synchronization of aim cells in optical ATM nodes

Claim 1

A method of time realignment of ATM cells in an optical ATM switching node, said method comprising the steps of: (a) passing an ATM cell to be realigned along an optical path from one switching element of said node with an original optical carrier; (b) recognizing a beginning of the ATM cell to be realigned and evaluating a time offset between said beginning and a reference instant; (c) converting said time offset into an error signal; (d) commanding with said error signal a transfer of said cell to a rephasing optical carrier; and (e) sending the cell and the rephasing optical carrier over a segment of predetermined length of an optical fiber with a high time dispersion, the rephasing optical carrier being of such wavelength that the cell reaches a subsequent switching element of the node at a predetermined instant.

Claim 2

A method of time realignment of ATM cells in an optical ATM switching node, said method comprising the steps of: (a) passing an ATM cell to be realigned along an optical path from one switching element of said node with an original optical carrier; (b) recognizing a beginning of the ATM cell to be realigned and evaluating a time offset between said beginning and a reference instant; (c) converting said time offset into an error signal; (d) commanding with said error signal a transfer of said cell to a rephasing optical carrier; and (e) sending the cell and the rephasing optical carrier over a segment of predetermined length of an optical fiber with a high time dispersion, the rephasing optical carrier being of such wavelength that the cell reaches a subsequent switching element of the node at a predetermined instant.

Claim 5

A method of time realignment of ATM cells in an optical ATM switching node, said method comprising the steps of: (a) passing an ATM cell to be realigned along an optical path from one switching element of said node with an original optical carrier; (b) recognizing a beginning of the ATM cell to be realigned and evaluating a time offset between said beginning and a reference instant; (c) converting said time offset into an error signal; (d) commanding with said error signal a transfer of said cell to a rephasing optical carrier; and (e) sending the cell and the rephasing optical carrier over a segment of predetermined length of an optical fiber with a high time dispersion, the rephasing optical carrier being of such wavelength that the cell reaches a subsequent switching element of the node at a predetermined instant, the recognition of the beginning of the cell comprising the steps of: effecting a series-to-parallel conversion of optical bits of the cell having a predetermined initial bit configuration, with a degree of parallelism equal to a number of bits in said initial configuration, detecting and converting into logic signals, each group of optical bits resulting from the series-to-parallel conversion comparing each group of logic signals with said initial configuration, and generating a signal of predetermined logic level when a comparison has a positive outcome.

Claim 6

A method of time realignment of ATM cells in an optical ATM switching node, said method comprising the steps of: (a) passing an ATM cell to be realigned along an optical path from one switching element of said node with an original optical carrier; (b) recognizing a beginning of the ATM cell to be realigned and evaluating a time offset between said beginning and a reference instant; (c) converting said time offset into an error signal; (d) commanding with said error signal a transfer of said cell to a rephasing optical carrier; and (e) sending the cell and the rephasing optical carrier over a segment of predetermined length of an optical fiber with a high time dispersion, the rephasing optical carrier being of such wavelength that the cell reaches a subsequent switching element of the node at a predetermined instant, the recognition of the beginning of the cell comprising the steps of: effecting a series-to-parallel conversion of optical bits of the cell having a predetermined initial bit configuration, with a degree of parallelism equal to a number of bits in said initial configuration, detecting and converting into logic signals, each group of optical bits resulting from the series-to-parallel conversion comparing each group of logic signals with said initial configuration, and generating a signal of predetermined logic level when a comparison has a positive outcome.

Claim 9

A device for time realignment of an ATM cell in an optical ATM cell in an optical ATM switching node where a cell to be realigned is sent into a segment of an optical fiber of a predetermined length with high time dispersion after being associated to a rephasing optical carrier of such a wavelength that affects the transient rate of the cell along the fiber so that the cell reaches an input of a subsequent switching element of the node at a predetermined instant, such device comprising: means for extracting a fraction of the optical signal associated to the cell to be realigned; means for recognizing the beginning of a cell, by utilizing the said fraction of the optical signal, and for generating a signal representative of the occurred recognition; means for receiving and comparing the signal representative of the occurred recognition of the beginning of the cell with a signal representative of a reference instant, and for generating an error signal indicative of the entity of the delay between the two signals; a tunable wavelength converter, driven by the said error signal, to transfer the cell to be realigned from an original carrier, to which the cell received by the device is associated, to the rephasing carrier for time dispersion in the optical fiber of predetermined length.

Claim 10

A device for time realignment of an ATM cell in an optical ATM cell in an optical ATM switching node where a cell to be realigned is sent into a segment of an optical fiber of a predetermined length with high time dispersion after being associated to a rephasing optical carrier of such a wavelength that affects the transient rate of the cell along the fiber so that the cell reaches an input of a subsequent switching element of the node at a predetermined instant, such device comprising: means for extracting a fraction of the optical signal associated to the cell to be realigned; means for recognizing the beginning of a cell, by utilizing the said fraction of the optical signal, and for generating a signal representative of the occurred recognition; means for receiving and comparing the signal representative of the occurred recognition of the beginning of the cell with a signal representative of a reference instant, and for generating an error signal indicative of the entity of the delay between the two signals; a tunable wavelength converter, driven by the said error signal, to transfer the cell to be realigned from an original carrier, to which the cell received by the device is associated, to the rephasing carrier for time dispersion in the optical fiber of predetermined length.

Claim 11

A device for time realignment of an ATM cell in an optical ATM cell in an optical ATM switching node where a cell to be realigned is sent into a segment of an optical fiber of a predetermined length with high time dispersion after being associated to a rephasing optical carrier of such a wavelength that affects the transient rate of the cell along the fiber so that the cell reaches an input of a subsequent switching element of the node at a predetermined instant, such device comprising: means for extracting a fraction of the optical signal associated to the cell to be realigned; means for recognizing the beginning of a cell, by utilizing the said fraction of the optical signal, and for generating a signal representative of the occurred recognition; means for receiving and comparing the signal representative of the occurred recognition of the beginning of the cell with a signal representative of a reference instant, and for generating an error signal indicative of the entity of the delay between the two signals; a tunable wavelength converter, driven by the said error signal, to transfer the cell to be realigned from an original carrier, to which the cell received by the device is associated, to the rephasing carrier for time dispersion in the optical fiber of predetermined length, said cell having a predetermined initial bit configuration and said means for recognizing said beginning of said cell comprising: a series to parallel converter for optical bits of the cell having as many outputs as equal the number of bits in said initial configuration, detection means connected to said converter for converting into logic electrical signals each group of optical bits exiting said series-to-parallel converter, and a comparison logic network for comparing each group of logic signals with said initial configuration and generating a signal at a predetermined positive outcome.

Claim 12

A device for time realignment of an ATM cell in an optical ATM cell in an optical ATM switching node where a cell to be realigned is sent into a segment of an optical fiber of a predetermined length with high time dispersion after being associated to a rephasing optical carrier of such a wavelength that affects the transient rate of the cell along the fiber so that the cell reaches an input of a subsequent switching element of the node at a predetermined instant, such device comprising: means for extracting a fraction of the optical signal associated to the cell to be realigned; means for recognizing the beginning of a cell, by utilizing the said fraction of the optical signal, and for generating a signal representative of the occurred recognition; means for receiving and comparing the signal representative of the occurred recognition of the beginning of the cell with a signal representative of a reference instant, and for generating an error signal indicative of the entity of the delay between the two signals; a tunable wavelength converter, driven by the said error signal, to transfer the cell to be realigned from an original carrier, to which the cell received by the device is associated, to the rephasing carrier for time dispersion in the optical fiber of predetermined length, said cell having a predetermined initial bit configuration and said means for recognizing said beginning of said cell comprising: a series to parallel converter for optical bits of the cell having as many outputs as equal the number of bits in said initial configuration, detection means connected to said converter for converting into logic electrical signals each group of optical bits exiting said series-to-parallel converter, and a comparison logic network for comparing each group of logic signals with said initial configuration and generating a signal at a predetermined positive outcome.