EP0499529A2
Expired / Lapsed
EP
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Optical loop back and line test apparatus
Assignee: NTT Inc
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Filing: 1992-02-11
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Granted: —
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Expires: 2012-02-11
Abstract
Abstract A testing apparatus is presented which evaluates the performance of optical signal transmissions in the 1.3 µm wavelength region, independently or simultaneously with signal transmission. An optical signal is transmitted in the network→user direction in a thermo-optic (TO) switch 11, and the signal is also looped in the direction A of an optical directional coupler 3. An optical time domain reflectometer (OTDR) 10 generates a test beam at 1.55 µm wavelength region, which is reflected by a wavelength selective filter 8 back to the OTDR 10 in the user→network direction. The apparatus is thus able to perform testing of the transmission cable 7 simultaneously with the signal transmission. When an operating problem is to be pinpointed in the system, the optical switch 11 is switched so as to permit the signal from a line terminal LT 1 to transmit in the network→user direction. The signal is attenuated by the same magnitude as the loss budget between the terminals NT 9 and LT1, and is looped back to LT 1, thereby enabling Loop 1 testing at the same signal strength level as in the actual signal transmission. At the same time, a test signal at 1.55 µm wavelength region is generated from the OTDR 10 in the network→user direction, and is reflected back to OTDR 10 in the user→network direction, thereby performing testing of the transmission cable 7. Loop C test can also be performed by following a similar procedure.
Inventors
- 👤 Toshiyuki Tsuchiya
- 👤 Jun Sato
- 👤 Kazuyoshi Ohno
- 👤 Satoyuki Matsui
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-29 03:06
CPC Classifications
H; H04; H04B; H04B10/00; H04B10/03; H04B10/035; H04B10/07; H04B10/071
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
326 words
An apparatus for evaluating the performance of a single cable bi-directional optical transmission system operating in a directional division multiplexing (DDM) mode, said system operating an optical signal transmission cable joining a line terminal and a network terminal, and transmitting an optical signal in a first wavelength region; said apparatus having: (a) an optical time domain reflectometer (OTDR) (10) operating a test beam in a second wavelength region; (b) a 1x2 optical directional coupler (3) provided with a first (PP!), a second (PP2), and a third (PP3) coupler terminals: wherein the coupling ratio is chosen so that the insertion loss between the first coupler terminal (PP1) and the second coupler terminal (PP2) is design to be low, and the insertion loss between the third coupler (PP3) terminal and the first coupler terminal (PP1) is designed to be slightly less than twice the loss budget between the line terminal (1) and the network terminal (12), and wherein the first coupler terminal (PP1) is connected to the user-side of the line terminal (1); and (c) a 2x2 optical switch having: a first (I), a second (II), a third (III) and a fourth (IV) switch terminals, wherein the first switch terminal (I) is connected to the second coupler terminal (PP2) of said 1x2 optical directional coupler (3), a teat beam generated by said OTDR (10) is inputted into the second switch terminal (II), and the third switch terminal (III) is connected to the third coupler terminal (PP3) of said 1x2 optical directional coupler (PP3) and the fourth switch terminal (IV) is connected to the transmission cable (7); wherein during the normal signal transmission mode, said first switch terminal (I) and second switch terminal (II) are both optically connected to said fourth switch terminal (IV), and a switch over operation is performed by optically connecting said first switch terminal (I) to said third switch terminal (III), and optically connecting said second switch terminal (II) to said fourth switch terminal (IV).
Claim 2
Dependent Claim
82 words
A loop back/line test apparatus as claimed in claim 1, wherein said 2x2 optical switch (11) is provided with a thermo-optic (TO) effect device fabricated integrally on a silicon substrate common with silicon waveguides, said device comprises a thin film heater (13) which, when electrical power to said heater (13) is turned on, alters the transmission terminal of said first wavelength region only, and said second wavelength region is transmitted through unaltered through the same terminal as when the power is off.
Claim 3
Independent Claim
391 words
An apparatus for evaluating the performance of a two cable bi-directional optical transmission system operating in a space division multiplexing (SDM) mode, said system operating an optical signal transmission cable joining a line terminal and a network terminal, and tranamitting an optical signal in a first wavelength region; said apparatus having: (a) an optical time domain reflectometer (OTDR) (10) generating a test beam in a second wavelength region; (b) a first 2x2 optical switch (11) having: a first (1a), a second (2a), a third (1b) and a fourth (2b) switch terminals, wherein during the normal signal transmission mode, the first (1a) and the second (2a) switch terminals are both optically connected to the third (1b) switch terminal, and in a switch over mode, the first (1a) and the second (2a) switch terminals are connected optically to the third (1b) and the fourth (2b) switch terminals, respectively, and a test beam generated by said OTDR (10) is inputted into the first (1a) switch terminals, and the second (2a) switch terminal is connected to an optical transmitter (OS) of said line terminal (1) and the third (1b) switch terminal is connected to the opposite end of the optical signal transmission cable (7) connected to said network terminal (9); (c) a second 2x2 optical switch (11) having: a fifth (3a), a sixth (4a), a seventh (3b) and eighth (4b) switch terminals, and wherein in the normal signal transmission mode, the fifth (3a) and sixth (4a) switch terminals are both optically connected to the eighth (4b) switch terminal, and during a switch over mode, the seventh (3b) and eighth (4b) switch terminals are, respectively, connected optically to the fifth (3a) and sixth (4a) switch terminals, respectively, wherein a test beam generated by said OTDR (10) is inputted into the sixth switch terminal (4a), and the fifth (3a) switch terminal is connected to an optical receiver (OR) terminal of said line terminal (1) and the eighth (4b) switch terminal is connected to the transmission cable (7); (d) an optical attenuator (6) inserted between the fourth (2b) switch terminal of said first 2x2 optical switch (11) and the seventh (3b) switch terminal of said second 2x2 optical switch (11); said attenuator (6) generating an attenuation magnitude which is slightly smaller than the signal attenuation in the transmission line between said line terminal (1) and network terminal (9).
Claim 4
Dependent Claim
81 words
A loop back/line test apparatus as claimed in claim 3, wherein said 2x2 optical switch is provided with a thermo-optic (TO) effect device fabricated integrally on a silicon substrate common with silicon waveguides, said device comprises a thin film heater (13) which, when electrical power to said heater (13) is turned on, alters the transmission terminal of said first wavelength region only, and said second wavelength region is transmitted through unaltered through the same terminal as when the power is off.
Claim 5
Independent Claim
270 words
An apparatus for evaluating the performance of a single cable bi-directional optical transmission system operating in a directional division multiplexing (DDM) mode, said system operating an optical signal transmission cable joining a line terminal and a network terminal, and transmitting an optical signal in a first wavelength region; said apparatus includes: (a) a 1x2 optical directional coupler (3) provided with a first (PP1), a second (PP2) and a third (PP3) coupler terminals wherein the first (PP1) coupler terminal is connected to a network-side of said network terminal (9); said directional coupler (3) having a coupling ratio chosen so that the insertion loss between the first (PP1) and second (PP2) coupler terminals is design to be low, and the insertion loss between the first (PP1) and third (PP3) coupler terminals is designed to be slightly less than twice the budget loss between the line terminal (1) and the network terminal (9), and (b) a 1x2 optical switch (13) having a first (I), a second (II), and a third (III) switch terminal; wherein the first (I) switch terminal is connected to said second (PP2) coupler terminal of said 1x2 optical directional coupler (3), and the second (II) switch terminal is connected to said third (PP3) coupler terminal of said 1x2 optical directional coupler (3) and said third (III) switch terminal is connected to the end of the opposite side of LT; wherein during the normal signal transmission mode, the first (PP1) switch terminal is connected optically with the third (PP3) switch terminal, and in a switch over mode, the first (I) switch terminal is optically connected with the second (II) switch terminal.
Claim 6
Dependent Claim
64 words
A loop back test apparatus as claimed in claim 5, wherein said 1x2 optical switch (11) is provided with a thermo-optic (TO) effect device fabricated integrally on a silicon substrate common with waveguides, said device comprises a thin film heater (13) having an on-state and an off-state, wherein the transmission behavior in said wavelength region is altered by said state of said heater (13).
Claim 7
Independent Claim
284 words
An apparatus for performing simultaneous loop back teat for a two cable bi-directional optical transmission system operating in a space division multiplexing (SDM) mode, transmitting a signal beam in two cables joining NT and LT; said apparatus having: (a) a first 1x2 optical switch (11) having: a first (3a), a second (4b) and a third (3b) switch terminals; wherein, in a normal signal transmiaaion mode, the first switch (3a) terminal is optically connected to the second (4b) switch terminal, and in a switch over mode, the first (3a) switch terminal is connected optically to the third (3b) switch terminal, and said first (3a) switch terminal is connected to an optical transmitter (OS) of said network terminal (9), and said second (4b) switch terminal is connected to the transmission cable (7); (b) a second 1x2 optical switch (11) having: a fourth (2a), a fifth ((2b) and a sixth (1b) switch terminals; wherein, in a normal signal transmission mode, the sixth (1b) switch terminal is connected optically to the fourth (2a) switch terminal, and in a switch over mode, the fifth (2b) switch terminal is connected optically to the fourth (2a) switch terminal, and the fourth (2a) switch terminal is connected to an optical receiver (OR) of said network terminal (9) and said sixth (1b) switch terminal is connected to the transmission cable (7); and (c) an optical attenuator (6) inserted between the third (3b) switch terminal of said first 1x2 optical switch (11) and said fifth (2b) switch terminal of said second 1x2 optical switch (11); said attenuator (6) generating an attenuation whose magnitude is slightly smaller than the loss budget in the transmission cable between said line terminal (1) and the network terminal (9).
Claim 8
Dependent Claim
64 words
A loop back/line test apparatus as claimed in claim 7, wherein said 1x2 optical switch (11) is provided with a thermo-optic (TO) effect device fabricated integrally on a silicon substrate common with waveguides, said device comprises a thin film heater (13) having an on-state and an off-state, wherein the transmission behavior in said wavelength region is altered by said state of said heater (13).
Claim 9
Dependent Claim
135 words
A loop back/line test apparatus as claimed in claim 1, wherein said 1x2 optical directional coupler (3) comprises a first waveguide and a second waveguide wherein a portion of said first and said second waveguides is made proximal to each other at a specific parallel distance, and the user-side of said first waveguide is connected to said first switch terminal (I) of said 2x2 optical switch (11), and the network-side of said first waveguide is connected to the user-side of said line terminal (1) the user-side of said second waveguide is connected to said third (III) switch terminal of said 2x2 optical switch (11), and the opposite open-end terminal of said second waveguide is sliced at an angle to the optic transmission path so as to prevent the Fresnel reflection from the surface (ES1) thereof.
Claim 10
Dependent Claim
135 words
A loop back/line test apparatus as claimed in claim 2, wherein said 1x2 optical directional coupler (3) comprises a first waveguide and a second waveguide wherein a portion of said first and said second waveguides is made proximal to each other at a specific parallel distance, and the user-side of said first waveguide is connected to said first switch terminal (I) of said 2x2 optical switch (11), and the network-side of said first waveguide is connected to the user-side of said line terminal (1) the user-side of said second waveguide is connected to said third (III) switch terminal of said 2x2 optical switch (11), and the opposite open-end terminal of said second waveguide is sliced at an angle to the optic transmission path so as to prevent the Fresnel reflection from the surface (ES1) thereof.
Claim 11
Dependent Claim
135 words
A loop back/line test apparatus as claimed in claim 5, wherein said 1x2 optical directional coupler (3) comprises a first waveguide and a second waveguide wherein a portion of said first and said second waveguides is made proximal to each other at a specific parallel distance, and the user-side of said first waveguide is connected to said first switch terminal (I) of said 2x2 optical switch (11), and the network-side of said first waveguide is connected to the user-side of said line terminal (1) the user-side of said second waveguide is connected to said third (III) switch terminal of said 2x2 optical switch (11), and the opposite open-end terminal of said second waveguide is sliced at an angle to the optic transmission path so as to prevent the Fresnel reflection from the surface (ES1) thereof.
Claim 12
Dependent Claim
134 words
A loop back/line test apparatus as claimed in claim 6, wherein said 1x2 optical directional coupler (3) comprises a first waveguide and a second waveguide wherein a portion of said first and said second waveguides is made proximal to each other at a specific parallel distance, and the user-side of said first waveguide is connected to said first (I) switch terminal of said 2x2 optical switch (11), and the network-side of said first waveguide is connected to the user-side of said line terminal (1) the user-side of said second waveguide is connected to said third (III) switch terminal of said 2x2 optical switch (11), and the opposite open-end terminal of said second waveguide is sliced at an angle to the optic transmission path so as to prevent the Fresnel reflection from the surface (ES1)thereof.
Claim 13
Dependent Claim
127 words
A loop back/line test apparatus as claimed in claim 3, wherein said optical attenuator (6) comprises a first and a second waveguides formed on a common silicon substrate, said waveguides in a parallel separation with each other to generate a coupling ratio dependent on said separation, wherein the input end of said first waveguide is connected to said fourth switch terminal of said first 2x2 optical switch (11), and the output end of said first waveguide, said output end outputting a desired magnitude of attenuation is connected to said seventh switch terminal of said second 2x2 optical switch (11), and both ends of said second waveguide are inclined at an angle to the optic transmission path so as to prevent the Fresnel reflection from the surfaces thereof.
Claim 14
Dependent Claim
146 words
A loop back/line test apparatus as claimed in claim 4, wherein said optical attenuator (6) comprises a first and a second waveguides formed on a common silicon substrate, said waveguides in a parallel separation with each other to generate a coupling ratio dependent on said separation, wherein the input end of said first waveguide is connected to said fourth (2b) switch terminal of said first 2x2 optical switch (11), and the output end of said first waveguide, said output end outputting a desired magnitude of attenuation is connected to said seventh (3b) switch terminal of said second 2x2 optical switch (11), and both ends of said second waveguide are inclined at an angle to the optic transmission path so as to second waveguide are inclined at an angle to the optic transmission path so as to prevent the Fresnel reflection from the surfaces (ES2, ES3) thereof.
Claim 15
Dependent Claim
134 words
A loop back/line test apparatus as claimed in claims 7, wherein said optical attenuator (6a) comprises a first and a second waveguides formed on a common silicon substrate 3, said waveguides in a parallel separation D with each other to generate a coupling ratio dependent on said separation D, wherein the input end of said first waveguide is connected to said fourth (2a) switch terminal of said first 2x2 optical switch (11), and the output end of said first waveguide, said output end outputting a desired magnitude of attenuation is connected to said seventh (3b) switch terminal of said second 2x2 optical switch (11), and both ends of said second waveguide are inclined at an angle to the optic transmission path so as to prevent the Fresnel reflection from the surfaces (ES2, ES3) thereof.
Claim 16
Dependent Claim
134 words
A loop back/line test apparatus as claimed in claims 8, wherein said optical attenuator (6a) comprises a first and a second waveguides formed on a common silicon substrate 3, said waveguides in a parallel separation D with each other to generate a coupling ratio dependent on said separation D, wherein the input end of said first waveguide is connected to said fourth (2a) switch terminal of said first 2x2 optical switch (11), and the output end of said first waveguide, said output end outputting a desired magnitude of attenuation is connected to said seventh (3b) switch terminal of said second 2x2 optical switch (11), and both ends of said second waveguide are inclined at an angle to the optic transmission path so as to prevent the Fresnel reflection from the surfaces (ES2, ES3) thereof.
Claim 17
Dependent Claim
56 words
A loop back/line test apparatus as claimed in claim 3, wherein said optical attenuator (6b) comprises a waveguide sliced and aligned at a distance by a specific separation distance, wherein slicing of the waveguide is made at an angle to said waveguide transmission path to prevent the Fresnel reflection from sliced open-end terminal surfaces (ES4, ES5).
Claim 18
Dependent Claim
56 words
A loop back/line test apparatus as claimed in claim 4, wherein said optical attenuator (6b) comprises a waveguide sliced and aligned at a distance by a specific separation distance, wherein slicing of the waveguide is made at an angle to said waveguide transmission path to prevent the Fresnel reflection from sliced open-end terminal surfaces (ES4, ES5).
Claim 19
Dependent Claim
56 words
A loop back/line test apparatus as claimed in claim 7, wherein said optical attenuator (6b) comprises a waveguide sliced and aligned at a distance by a specific separation distance, wherein slicing of the waveguide is made at an angle to said waveguide transmission path to prevent the Fresnel reflection from sliced open-end terminal surfaces (ES4, ES5).
Claim 20
Dependent Claim
56 words
A loop back/line test apparatus as claimed in claim 8, wherein said optical attenuator (6b) comprises a waveguide sliced and aligned at a distance by a specific separation distance, wherein slicing of the waveguide is made at an angle to said waveguide transmission path to prevent the Fresnel reflection from sliced open-end terminal surfaces (ES4, ES5).
References Cited (Backward Citations)
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