A -- Technology for Agile Coherent Optical Transmission Architecture (TACOTA)

This is a modification to the BAA 05-36 entitled Technology for Agile Coherent Optical Transmission Architecture (TACOTA) which was posted on April 26, 2005. You are notified that the following changes are made: Proposal due date is revised to August 26, 2005. Areas of interest are revised as described below. Program scope is revised as described below. Areas of Interest Modifications to the original BAA are made in the individual areas of interest as follows. I. 1550 nm Coherent Optical Transmitter & Receiver Technology This modification clarifies the definition of receiver sensitivity that is discussed in the original BAA. Sensitivity is defined as the number of fiber-coupled 1550 nm photons per bit at the TACOTA receiver input required to achieve the desired bit error rate. It is recommended that proposals include optical power budgets for TACOTA receivers that provide estimated optical losses referenced to fiber-coupled 1550 nm optical power in the single-mode fiber at the receiver input. Although sensitivity is characterized by 1550 nm photons, receiver sensitivity calculations and analyses should include any effects resulting from two-way (up and down-conversion) wavelength translation. II. Phase-Sensitive Wavelength Translation Technology This modification is revised so that 1550 nm intra-band wavelength translation is no longer within the development scope of TACOTA. Additionally, offerors need only address one of the remaining cited translation bands. That is, successful offerors will develop and demonstrate one of the following two wavelength translation scenarios: (1) phase-sensitive translation between the 1550/500 nm bands; or (2) phase-sensitive translation between the 1550/3800 nm bands. Offerors who choose to include both translation scenarios are encouraged to provide a cost breakdown that itemizes the two efforts. III. Application-based Link Demonstration This modification downscopes the level of effort required to test system-level TACOTA performance. Offerors need only execute laboratory-based testing sufficient to demonstrate system-level TACOTA link performance targets, as additional more rigorous testing will take place at government laboratory facilities. It is not imperative that TACOTA equipment be fully ruggedized; equipment should be transportable with minimal need for recalibration and be able to be easily configured and integrated with other components and/or the testbed. TACOTA links will be tested over various ranges both with and without receive adaptive optics correction. These links will be evaluated to determine bit error rate, sensitivity, throughput and the ability to handle atmospheric impairments. Proposals should address transmission impairments relevant to free-space optical communications, as well as potential design paths to alleviate such effects. Implementation of these mitigation approaches is not necessarily required as part of the TACOTA program. In particular, transmission through either the atmosphere or through water introduces both longitudinal and transverse phase aberrations to a coherent optical communication beam. Longitudinal phase aberrations change the overall optical phase of the beam on a timescale of hundreds of Hertz, which affects the receivers ability to both amplify and extract the information in the beam. Transverse aberrations will change the optical phase across the wavefront, thus limiting the size of the receive aperture over which the received beam can be considered to be coherent. Transverse aberrations have the effect of reducing the coupling efficiency into single mode fiber and dramatically increasing scintillation over that seen in incoherent free-space optical systems, which generally use multimode fiber receivers. Both longitudinal and transverse phase aberrations are highly path-dependent and their effects should be carefully considered in developing proposal responses to the BAA. Program Scope This modification specifies the length of the Program development phases. The TACOTA program will consist of a 18 month Phase I effort with Go Ahead critical milestones at the end of 15 months. This will be followed by a 18-month Phase II option to achieve the full performance targets. Offerors should provide a plan to meet all the performance metrics specified in the BAA or a clear justification of why the performance metric(s) cannot be met. These performance targets should be included in Enclosure 2 and should reflect the performance goals established in Section I. Point of Contact S. Pappert, DARPA Program Manager, Phone (571) 218-4679, Fax (703) 696-2206, Email spappert@darpa.mil