Description of Business	12 Months Ended
Sep. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business	Description of Business Business Overview EMCORE Corporation (referred to herein, together with its subsidiaries, as the “Company,” “we,” “our,” or “EMCORE”) was established in 1984 as a New Jersey corporation. The Company became publicly traded in 1997 and is listed on the Nasdaq stock exchange under the ticker symbol EMKR. EMCORE pioneered the linear fiber optic transmission technology that enabled the world’s first delivery of Cable TV directly on fiber, and today is a leading provider of advanced Mixed-Signal Optics products that enable communications systems and service providers to meet growing demand for increased bandwidth and connectivity. The Mixed-Signal Optics technology at the heart of our broadband communications products is shared with our fiber optic gyros and inertial sensors to provide the aerospace and defense markets with state-of-the-art navigation systems technology. With both analog and digital circuits on multiple chips, or even a single chip, the value of Mixed-Signal device solutions is often far greater than traditional digital applications and requires a specialized expertise held by EMCORE which is unique in the optics industry. We currently have one reporting segment: Fiber Optics. This segment is comprised of three product lines: Broadband (which includes Cable TV (“CATV”) systems and components, radio frequency over glass (“RFoG”) products, satellite/microwave communications products and wireless communication products), Chip Devices and Navigation Systems. Sale of Photovoltaics and Digital Products Businesses In the fiscal year ended September 30, 2015, EMCORE completed the sale of the Company's Photovoltaics Business to SolAero Technologies Corporation (“SolAero”) pursuant to the Asset Purchase Agreement (the “Photovoltaics Agreement”) under which SolAero acquired substantially all of the assets, and assumed substantially all of the liabilities, primarily related to or used in connection with the Company's Photovoltaics Business, including EMCORE's subsidiaries EMCORE Solar Power, Inc. and EMCORE IRB Company, LLC (collectively, the “Photovoltaics Business” and, the sale of the Photovoltaics Business, the “Photovoltaics Asset Sale”), for $149.9 million in cash. In the fiscal year ended September 30, 2015, EMCORE completed the sale of the Company's telecommunications business (the “Digital Products Business”) to NeoPhotonics Corporation, a Delaware corporation (“NeoPhotonics”), pursuant to the Asset Purchase Agreement (the “Digital Products Agreement”), under which NeoPhotonics acquired certain assets, and certain liabilities, related to the Company's Digital Products Business for an aggregate purchase price of $17.5 million. On January 2, 2015, EMCORE completed the sale of the Digital Products Business for $1.5 million in cash and a promissory note in the principal amount of $16.0 million (the "Promissory Note"). On April 16, 2015, EMCORE and NeoPhotonics entered into an agreement to adjust the purchase price for the Digital Products Business, resulting in an adjusted balance of the Promissory Note of $15.5 million. On April 17, 2015, NeoPhotonics paid in full the outstanding balance of the Promissory Note of $15.5 million, plus accrued interest of $0.2 million. No Photovoltaics Business or Digital Products Business assets or liabilities that were sold remain on the consolidated balance sheet as of September 30, 2018 or September 30, 2017. The financial results of the Photovoltaics Business and the Digital Products Business are presented as “discontinued operations” on the consolidated statements of operations and comprehensive income for the fiscal years ended September 30, 2018, 2017 and 2016. See Note 5 - Discontinued Operations for additional information. The notes to our consolidated financial statements relate to our continuing operations only, unless otherwise indicated.

Description of Business

Business Overview

EMCORE Corporation (referred to herein, together with its subsidiaries, as the “Company,” “we,” “our,” or “EMCORE”) was established in 1984 as a New Jersey corporation. The Company became publicly traded in 1997 and is listed on the Nasdaq stock exchange under the ticker symbol EMKR. EMCORE pioneered the linear fiber optic transmission technology that enabled the world’s first delivery of Cable TV directly on fiber, and today is a leading provider of advanced Mixed-Signal Optics products that enable communications systems and service providers to meet growing demand for increased bandwidth and connectivity. The Mixed-Signal Optics technology at the heart of our broadband communications products is shared with our fiber optic gyros and inertial sensors to provide the aerospace and defense markets with state-of-the-art navigation systems technology. With both analog and digital circuits on multiple chips, or even a single chip, the value of Mixed-Signal device solutions is often far greater than traditional digital applications and requires a specialized expertise held by EMCORE which is unique in the optics industry.

We currently have one reporting segment: Fiber Optics. This segment is comprised of three product lines: Broadband (which includes Cable TV (“CATV”) systems and components, radio frequency over glass (“RFoG”) products, satellite/microwave communications products and wireless communication products), Chip Devices and Navigation Systems.

Sale of Photovoltaics and Digital Products Businesses

In the fiscal year ended September 30, 2015, EMCORE completed the sale of the Company's Photovoltaics Business to SolAero Technologies Corporation (“SolAero”) pursuant to the Asset Purchase Agreement (the “Photovoltaics Agreement”) under which SolAero acquired substantially all of the assets, and assumed substantially all of the liabilities, primarily related to or used in connection with the Company's Photovoltaics Business, including EMCORE's subsidiaries EMCORE Solar Power, Inc. and EMCORE IRB Company, LLC (collectively, the “Photovoltaics Business” and, the sale of the Photovoltaics Business, the “Photovoltaics Asset Sale”), for $149.9 million in cash.

In the fiscal year ended September 30, 2015, EMCORE completed the sale of the Company's telecommunications business (the “Digital Products Business”) to NeoPhotonics Corporation, a Delaware corporation (“NeoPhotonics”), pursuant to the Asset Purchase Agreement (the “Digital Products Agreement”), under which NeoPhotonics acquired certain assets, and certain liabilities, related to the Company's Digital Products Business for an aggregate purchase price of $17.5 million. On January 2, 2015, EMCORE completed the sale of the Digital Products Business for $1.5 million in cash and a promissory note in the principal amount of $16.0 million (the "Promissory Note"). On April 16, 2015, EMCORE and NeoPhotonics entered into an agreement to adjust the purchase price for the Digital Products Business, resulting in an adjusted balance of the Promissory Note of $15.5 million. On April 17, 2015, NeoPhotonics paid in full the outstanding balance of the Promissory Note of $15.5 million, plus accrued interest of $0.2 million.

No Photovoltaics Business or Digital Products Business assets or liabilities that were sold remain on the consolidated balance sheet as of September 30, 2018 or September 30, 2017. The financial results of the Photovoltaics Business and the Digital Products Business are presented as “discontinued operations” on the consolidated statements of operations and comprehensive income for the fiscal years ended September 30, 2018, 2017 and 2016. See Note 5 - Discontinued Operations for additional information. The notes to our consolidated financial statements relate to our continuing operations only, unless otherwise indicated.