Balance Sheet Components (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Dec. 26, 2015	Dec. 27, 2014	Dec. 26, 2015	Dec. 27, 2014	Jun. 27, 2015
Accounts receivable allowance
Accounts receivable allowance	$ 0.7		$ 0.7		$ 1.2
Inventories
Finished goods	50.8		50.8		60.1
Work in process	26.3		26.3		23.4
Raw materials and purchased parts	30.2		30.2		16.2
Inventories, net	107.3		107.3		99.7
Inventory written off	0.6	$ 1.4	1.1	$ 2.0
Prepayments and other current assets
Prepayments	28.5		28.5		20.4
Advances to contract manufacturers	8.7		8.7		9.5
Due from Viavi, net	1.0		1.0		0.0
Other current assets	12.2		12.2		16.2
Prepayments and other current assets	50.4		50.4		46.1
Property, plant and equipment
Property, plant and equipment, gross	464.9		464.9		416.2
Less: Accumulated depreciation	(313.5)		(313.5)		(273.0)
Property, plant and equipment, net	151.4		151.4		143.2
Other current liabilities
Restructuring accrual and related charges	4.3		4.3		3.2
Warranty accrual	3.1		3.1		2.8
Others	4.4		4.4		5.4
Other current liabilities	11.8		11.8		11.4
Other non-current liabilities
Asset retirement obligation	2.1		2.1		1.8
Pension and related accruals	2.6		2.6		2.1
Deferred rent	1.5		1.5		1.7
Restructuring accrual and related charges	0.0		0.0		1.7
Other non-current liabilities	1.8		1.8		2.5
Total other non-current liabilities	8.0		8.0		9.8
Land
Property, plant and equipment
Property, plant and equipment, gross	5.9		5.9		5.9
Buildings and improvements
Property, plant and equipment
Property, plant and equipment, gross	28.7		28.7		28.6
Machinery and equipment
Property, plant and equipment
Property, plant and equipment, gross	335.2		335.2		326.4
Furniture and fixtures and software
Property, plant and equipment
Property, plant and equipment, gross	31.4		31.4		8.0
Leasehold improvements
Property, plant and equipment
Property, plant and equipment, gross	28.7		28.7		20.5
Construction in progress
Property, plant and equipment
Property, plant and equipment, gross	$ 35.0		$ 35.0		$ 26.8