Optical waveguides – With optical coupler – Switch
Reexamination Certificate
1999-12-14
2001-08-21
Sanghavi, Hemang (Department: 2874)
Optical waveguides
With optical coupler
Switch
C385S016000, C385S017000, C385S019000, C385S024000, C385S089000
Reexamination Certificate
active
06278812
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to optical networks. In particular, the present invention relates to a device and method for achieving protection in the case of mirror failure in free-space micromachined optical switches.
BACKGROUND INFORMATION
With the growing capacity demand for optical fiber communications, optical crossconnects (“OXCs”) with hundreds of ports are expected to become essential components of future optical transport networks within three to five years. This requirement in port count far outstrips the demonstrated capabilities of current deployable technology. Conventional mechanical switches suffer from large size, large element mass and slow switching time. On the other hand, guided-wave solid-state switches show limited expandability due to their high loss, high crosstalk and long device length.
Recently, free-space micromachined optical switching technology has been proposed as a means of building large optical crossconnects. This technology features the advantages of free-space interconnection, chiefly low loss and low crosstalk, while retaining the compactness and batch-fabrication economy of monolithic integration. Furthermore, the sub-millisecond switching times are well matched to the needs of OXCs in optical transport networks.
With the increasing capacity demand and complexity of optical networks, restoring network traffic promptly in the event of fiber failure becomes an important issue for network control and management. Optical crossconnects have been proposed as promising candidates for provisioning and restoration in optical networks at wavelength levels. In addition to protecting fiber failures, the optical crossconnect should also have protection schemes for itself so that its functionality will not be interrupted when one or more of its switching elements malfunctions.
Recent developments have focused on free-space micro-machined optical switches to achieve the optical performance and capacity requirement for optical crossconnects in multi-wavelength optical networks. The switch fabric includes micromachined free-rotating mirrors as switching elements. Backsides of the mirrors have also been used to achieve connection-symmetry in optical networks.
SUMMARY OF THE INVENTION
The present invention provides a device and method for achieving protection in a free-space micromachined optical switching fabric. The present invention provides two protection schemes for mirror failures, which utilize either existing switching mirrors or additional integrated mirrors without extra fabrication effort or performance-degradation of the switch fabric. A switch fabric includes a plurality of micromachined free-rotating mirrors arranged in a rectilinear matrix configuration. The mirrors are reflective on both front and back sides. According to one embodiment of the present invention, upon the detection of a failed mirror associated with a transmission between an input and an output, a transmission path is determined that includes a backside of a pivot mirror. A transmission path is then established between the input and the output that utilizes the backside of the pivot mirror.
According to one embodiment, the switching fabric utilizes M×N mirrors arranged in a rectilinear matrix configuration of M columns and N rows. Upon the detection of a mirror failure associated with a column Fc and a row Fr (mirror (Fc, Fr)), a pivot mirror is determined, wherein the pivot mirror is any actuated mirror having located in a column Pc and row Pr, wherein Pc<Fc and Pr<Fr. A first mirror at location (Fc,Pr) and a second mirror at location (Pc,Fr) are then actuated to perform the necessary routing.
According to an alternative embodiment, at least one protection row of switch mirrors and at least one protection column of switch mirrors is coupled to a rectilinear switch fabric. Upon detection of a mirror failure, a transmission path associated with the failed mirror is established by actuating mirrors in the protection row and protection column. In particular, according to one alternative embodiment, the present invention is applied to a rectilinear switch fabric of M×N micromirrors arranged in M columns and N rows. A series of input ports are provided along a first side of the switch fabric and a series of output ports are provided along a second side of the switch fabric perpendicular to the first side. According to the present invention, at least one protection row of mirrors is coupled between the input ports and the switch fabric and at least one protection column of mirrors is coupled between the output ports and the switch fabric, wherein the protection row includes a pivot mirror that is also co-located in the protection column. The pivot mirror is placed in a permanently actuated state. Upon detection of a mirror failure at location (Fc,Fr), a mirror in the protection row at location Fc is actuated and a mirror in the protection column at location Fr is actuated to form a transmission path from the input to the output via the pivot mirror.
REFERENCES:
patent: 5208880 (1993-05-01), Riza et al.
patent: 5960132 (1999-09-01), Lin
patent: 6002818 (1999-12-01), Fatchi et al.
patent: 6058130 (2000-05-01), Shinji et al.
Lin Lih Y.
Saleh Adel A. M.
Simmons Jane M.
AT&T Corporation
Doan Jennifer
Kenyon & Kenyon
Sanghavi Hemang
LandOfFree
Protection schemes for mirror-failure in free-space... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Protection schemes for mirror-failure in free-space..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Protection schemes for mirror-failure in free-space... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2489763