Operating Segments and Geographic Information - Information on Reportable Segments (Details) $ in Millions	3 Months Ended		9 Months Ended
	Mar. 30, 2019 USD ($)	Mar. 31, 2018 USD ($)	Mar. 30, 2019 USD ($) segment	Mar. 31, 2018 USD ($)
Information on reportable segments
Number of broad business categories (in segment) | segment			2
Total net revenue	$ 265.2	$ 218.7	$ 840.6	$ 615.0
Gross profit	$ 153.5	$ 123.3	$ 481.9	$ 355.4
Gross margin (as a percent)	57.90%	56.40%	57.30%	57.80%
Operating income	$ 7.9	$ 0.4	$ 39.6	$ 14.0
Operating margin (as a percent)	3.00%	0.20%	4.70%	2.30%
Other Items
Information on reportable segments
Total net revenue	$ 0.0	$ 0.0	$ 0.0	$ 0.0
Gross profit	(9.0)	(10.7)	(29.0)	(23.3)
Operating income	(31.1)	(32.8)	(107.1)	(73.9)
Network and Service Enablement | Segment Measures
Information on reportable segments
Total net revenue	205.4	156.4	619.8	450.1
Gross profit	$ 131.7	$ 101.2	$ 398.9	$ 288.3
Gross margin (as a percent)	64.10%	64.70%	64.40%	64.10%
Operating income	$ 20.7	$ 9.5	$ 69.9	$ 24.6
Operating margin (as a percent)	10.10%	6.10%	11.30%	5.50%
Network and Service Enablement | Network Enablement | Segment Measures
Information on reportable segments
Total net revenue	$ 180.5	$ 126.5	$ 540.5	$ 360.1
Gross profit	$ 115.8	$ 80.4	$ 344.4	$ 225.1
Gross margin (as a percent)	64.20%	63.60%	63.70%	62.50%
Network and Service Enablement | Service Enablement | Segment Measures
Information on reportable segments
Total net revenue	$ 24.9	$ 29.9	$ 79.3	$ 90.0
Gross profit	$ 15.9	$ 20.8	$ 54.5	$ 63.2
Gross margin (as a percent)	63.90%	69.60%	68.70%	70.20%
Optical Security and Performance Products | Segment Measures
Information on reportable segments
Total net revenue	$ 59.8	$ 62.3	$ 220.8	$ 164.9
Gross profit	$ 30.8	$ 32.8	$ 112.0	$ 90.4
Gross margin (as a percent)	51.50%	52.60%	50.70%	54.80%
Operating income	$ 18.3	$ 23.7	$ 76.8	$ 63.3
Operating margin (as a percent)	30.60%	38.00%	34.80%	38.40%
Product
Information on reportable segments
Total net revenue	$ 232.1	$ 193.2	$ 746.0	$ 539.6
Product | Other Items
Information on reportable segments
Total net revenue	0.0	0.0	0.0	0.0
Product | Network and Service Enablement | Segment Measures
Information on reportable segments
Total net revenue	172.4	131.4	525.7	376.4
Product | Network and Service Enablement | Network Enablement | Segment Measures
Information on reportable segments
Total net revenue	160.8	116.0	486.7	333.3
Product | Network and Service Enablement | Service Enablement | Segment Measures
Information on reportable segments
Total net revenue	11.6	15.4	39.0	43.1
Product | Optical Security and Performance Products | Segment Measures
Information on reportable segments
Total net revenue	59.7	61.8	220.3	163.2
Service
Information on reportable segments
Total net revenue	33.1	25.5	94.6	75.4
Service | Other Items
Information on reportable segments
Total net revenue	0.0	0.0	0.0	0.0
Service | Network and Service Enablement | Segment Measures
Information on reportable segments
Total net revenue	33.0	25.0	94.1	73.7
Service | Network and Service Enablement | Network Enablement | Segment Measures
Information on reportable segments
Total net revenue	19.7	10.5	53.8	26.8
Service | Network and Service Enablement | Service Enablement | Segment Measures
Information on reportable segments
Total net revenue	13.3	14.5	40.3	46.9
Service | Optical Security and Performance Products | Segment Measures
Information on reportable segments
Total net revenue	$ 0.1	$ 0.5	$ 0.5	$ 1.7