Optical repeater having means for preventing malfunction due to the presence of noise

Claim 2

An optical repeater provided in an up line (66a) and a down line (66b), said optical repeater including: a first circuit (1, 60a, 16-20) related to said up line; and a second circuit (2, 60b, 16-20) related to said down line, characterized in that each of said first circuit and said second circuit comprises: input means (1, 2) for receiving an optical input via a corresponding one of said up line and said down line and for converting said optical input into an electrical signal including a data signal and a command signal; command extracting means (61a, 61b), coupled to said input means, for extracting a command signal from said electrical signal; command detecting means (63a, 63b), coupled to said command extracting means, for generating a command detection signal when said command extracting means extracts said command signal; command switching means (64a, 64b), coupled to said command extracting means, for selecting one of said command signal extracted by said command extracting means of said first circuit and said command signal extracted by said command extracting means of said second circuit in response to said command detection signal; supervising means (65a, 65b), coupled to said command switching means, for generating a supervisory signal indicative of an operating state of said optical repeater in response to said command signal selected by said command switching means; noise component processing means (62a, SWa, 62b, SWb), operably coupled to said input means, said command extracting means, said command detecting means and said command switching means, for extracting, from said electrical signal, a noise component within a predetermined frequency range excluding a frequency (f₁) of said command signal and determining whether or not said optical signal is input to said input means on the basis of said noise component and for preventing said noise component passing through said command extracting means from being directly applied to said command detecting means when it is determined that no said optical input is input to said input means; and output means (16-20), coupled to said input means and said supervising means, for converting said data signal and said supervisory signal into an optical output which is transferred to a corresponding one of the up line and the down line.

Claim 3

An optical repeater provided in an up line (66a) and a down line (66b), said optical repeater including: a first circuit (1, 60a, 16-20) related to said up line; and a second circuit (2, 60b, 16-20) related to said down line, characterized in that each of said first circuit and said second circuit comprises: input means (1, 2) for receiving an optical input via a corresponding one of said up line and said down line and for converting said optical input into an electrical signal including a data signal and a command signal; command extracting means (61a, 61b), coupled to said input means, for extracting a command signal from said electrical signal; command detecting means (63a, 63b), coupled to said command extracting means, for generating a command detection signal when said command extracting means extracts said command signal; command switching means (64a, 64b), coupled to said command extracting means, for selecting one of said command signal extracted by said command extracting means of said first circuit and said command signal extracted by said command extracting means of said second circuit in response to said command detection signal and a switching control signal; supervising means (65a, 65b), coupled to said command switching means, for generating a supervisory signal indicative of an operating state of said optical repeater in response to said command signal selected by said command switching means; noise component processing means (62a, 62b), operably coupled to said input means, said command extracting means, said command detecting means and said command switching means, for extracting, from said electrical signal, a noise component within a predetermined frequency range excluding a frequency (f₁) of said command signal and determining whether or not said optical signal is input to said input means on the basis of said noise component and for generating said switching control signal when it is determined that no said optical input is input to said input means; and output means (16-20), coupled to said input means and said supervising means, for converting said data signal and said supervisory signal into an optical output which is transferred to a corresponding one of the up line and the down line, wherein: said command switching means (64a) of said first circuit selects said command signal extracted by said command extracting means (61b) of said second circuit when receiving said switching control signal irrespective of the presence of said command detection signal output by said command detecting means (63a) of said first circuit; and said command switching means (64b) of said second circuit selects said command signal extracting by said command extracting means (61b) of said first circuit when receiving said switching control signal irrespective of the presence of said command detection signal output by said command detecting means (63b) of said second circuit.

Claim 4

An optical repeater provided in an up line (66a) and a down line (66b), said optical repeater including: a first circuit (1, 60a, 16-20) related to said up line; and a second circuit (2, 60b, 16-20) related to said down line, characterized in that each of said first circuit and said second circuit comprises: input means (1, 2) for receiving an optical input via a corresponding one of said up line and said down line and for converting said optical input into an electrical signal including a data signal and a command signal; command extracting means (61a, 61b), coupled to said input means, for extracting a command signal from said electrical signal; command detecting means (63a, 63b), coupled to said command extracting means, for generating a command detection signal when said command extracting means extracts said command signal; command switching means (64a, 64b), coupled to said command extracting means, for selecting one of said command signal extracted by said command extracting means of said first circuit and said command signal extracted by said command extracting means of said second circuit in response to said command detection signal and a switching control signal; supervising means (65a, 65b), coupled to said command switching means, for generating a supervisory signal indicative of an operating state of said optical repeater in response to said command signal selected by said command switching means; noise component processing means (62a, 62b), operably coupled to said input means, said command extracting means, said command detecting means and said command switching means, for extracting, from said electrical signal, a noise component within a predetermined frequency range excluding a frequency (f₁) of said command signal and determining whether or not said optical signal is input to said input means on the basis of said noise component and for generating said switching control signal when it is determined that no said optical input is input to said input means; and output means (16-20), coupled to said input means and said supervising means, for converting said data signal and said supervisory signal into an optical output which is transferred to a corresponding one of the up line and the down line, wherein: said command switching means (64a) of said first circuit selects said command signal extracted by said command extracting means (61b) of said second circuit when receiving said switching control signal irrespective of the presence of said command detection signal output by said command detecting means (63a) of said first circuit; and said command switching means (64b) of said second circuit selects said command signal extracting by said command extracting means (61b) of said first circuit when receiving said switching control signal irrespective of the presence of said command detection signal output by said command detecting means (63b) of said second circuit.

Claim 5

An optical repeater as claimed in claim 1 or 2, characterized in that: said command switching means (64a) of said first circuit selects said command signal extracted by said command extracting means (61b) of said second circuit when said command detecting means (63a) of said first circuit does not output said command detection signal; and said command switching means (64b) of said second circuit selects said command signal extracted by said command extracting means (61a) of said first circuit when said command detecting means (63b) of said second circuit does not output said command detection signal.

Claim 6

An optical repeater as claimed in claim 1 or claim 3, characterized in that said noise component processing means in each of said first circuit and said second circuit comprises connection switching means (SWa, SWb), provided between said command extracting means (61a, 61b) and said command detecting means (63a, 63b), for disconnecting said command detecting means from said command extracting means when it is determined, by said noise component processing means, that no said optical signal is input to said input means.

Claim 7

An optical repeater as claimed in any of claims 1 to 4, characterized in that said noise component processing means in each of said first circuit and said second circuit comprises: filter means (62a-1) for extracting said noise component from said electrical signal; and comparator means (62a-2) for comparing a level of said noise component extracted by said filter means with a predetermined threshold level (TH) and for generating a control signal when said noise component within said predetermined frequency range has a level higher than said predetermined threshold level, and in that said control signal indicates that no said optical input is input to said input means.

Claim 8

An optical repeater as claimed in any of claims 2, 3 or 5, characterized by further comprising inhibit means (69a) for inhibiting said command detection signal from being sent to said command switching means (64a, 64b) when said noise component processing means generates said switching control signal.

Claim 9

An optical repeater as claimed in claim 5, characterized in that: said control signal generated by said comparator means (62a-2) is added to said noise component passing through said command extracting means (61a) so that said noise component passing through said command extracting means is prevented from being applied to said command detecting means (63a) when no said optical input is input to said input means.

Claim 10

An optical repeater as claimed in claim 5, characterized in that: said command detecting means (63a) comprises comparing means (63a-3) for comparing a level of said command signal with a command detection threshold level (Lth) and for generating said command detection signal when the level of said command signal is higher than said command detection threshold level; said control signal generated by said comparator means (62a-2) is added to said noise component passing through said command extracting means (61a); and said optical repeater further comprises amplifier means (63a-1) for amplifying said noise signal with said control signal added thereto and for outputting a logic level which is lower than said command detection threshold level.

Claim 11

An optical repeater as claimed in any of claims 1 to 8, characterized in that said noise component processing means comprises a bandpass filter (62a-1, BPF) having a bandpass frequency range which is higher than zero and which is lower than the frequency (f₁) of said command signal.

Claim 12

An optical repeater as claimed in any of claims 1 to 8, characterized in that said noise component processing means comprises a lowpass filter (62a-1, LPF) having a lowpass frequency range lower than the frequency (f₁) of said command signal.

Claim 13

An optical repeater as claimed in claim 9, characterized in that said noise component processing means comprises noise level comparing means (62a-2) for comparing the level of said noise component extracted by said bandpass filter with a predetermined threshold level (TH) to thereby generate a comparison result and for determining, on the basis of said comparison result, whether or no optical input is input to said input means.

Claim 14

An optical repeater as claimed in claim 10, characterized in that said noise component processing means comprises noise level comparing means (62a-2) for comparing the level of said noise component extracted by said lowpass filter with a predetermined threshold level (TH) to thereby generate a comparison result and for determining, on the basis of said comparison result, whether or no optical input is input to said input means.

Claim 15

An optical repeater as claimed in claim 10, characterized in that said noise component processing means comprises noise level comparing means (62a-2) for comparing the level of said noise component extracted by said lowpass filter (62a-1, LPF) with a predetermined threshold level (TH) to thereby generate a comparison result and for generating, on the basis of said comparison result, said switching control signal indicating whether or no optical input is input to said input means.

Claim 16

An optical repeater as claimed in any of claims 1 to 8, characterized in that said noise component processing means comprises a first bandpass filter (62a-1, BPF) having a bandpass frequency range which is higher than zero and which is lower than the frequency (f₁) of said command signal and a second bandpass filter (62a-1, BPF) having a bandpass range which is higher than the frequency (f₁) of said command signal and which is lower than a predetermined frequency (f₂) higher than the frequency of said command signal.

Claim 17

An optical repeater as claimed in any of claims 1 to 8, characterized in that said noise component processing means comprises a bandpass filter (62a-1, BPF) having a bandpass frequency range (f₂-f₃) in which said noise component obtained when no said optical input is input to said input means has a level lower than that obtained when said optical input is input to said input means.

Claim 18

An optical repeater as claimed in any of claims 1 to 8, characterized in that said noise component processing means comprises a highpass filter (62a-1, HPF) having a highpass frequency range (>f₂) in which said noise component obtained when no said optical input is input to said input means has a level lower than that obtained when said optical input is input to said input means.

Claim 19

An optical repeater as claimed in claim 15 or 16, characterized in that said noise component processing means comprises noise level comparing means (62a-1) for comparing the level of said noise component extracted by said bandpass filter with a predetermined threshold level (TH) to thereby generate a comparison result and for determining, on the basis of said comparison result, whether or no optical input is input to said input means.

Claim 20

An optical repeater as claimed in claim 15 or 16, characterized in that said noise component processing means comprises noise level comparing means (62a-2) for comparing the level of said noise component extracted by said bandpass filter with a predetermined threshold level (TH) to thereby generate a comparison result and for generating, on the basis of said comparison result, said switching control signal indicating whether or no optical input is input to said input means.

Claim 21

An optical repeater as claimed in claim 17 or 18, characterized in that said predetermined threshold level (TH) is higher than a level (C2) of said noise component obtained when no said optical input is input to said input means and lower than a level (C1) of said noise component obtained when said optical input is input to said input means.

Claim 22

An optical repeater as claimed in any of claims 1 to 19, characterized in that said input means comprises equalizing means (12) for equalizing said electrical signal and generating an equalized electrical signal, timing generating means (14) for generating a timing signal from said equalized electrical signal and decision means (13) for reshaping said equalized electrical signal in synchronism with said timing signal.

Claim 23

An optical repeater as claimed in any of claims 1 to 20, characterized in that: said electrical signal is grouped into blocks each having a predetermined number of bits including data bits and a parity bit (P); said command signal is formed by an odd parity bit (O) arranged in said blocks at predetermined intervals.